DESC:FIELD
The present disclosure relates to a laminate and a process for its preparation. Particularly, the present disclosure relates to a laminate based on crotonaldehyde.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Pre-preg: The term ‘pre-preg’ refers to a fibrous material pre-impregnated with a particular synthetic resin, used in making reinforced plastics.
Laminates: The term ‘laminates’ refers to plastic materials made by bonding two or more sheets of pre-preg materials or resin-impregnated fibrous sheets together, usually with heat and pressure.
ABBREVIATIONS:
PF: Phenol formaldehyde
PC: Phenol crotonaldehyde
PC3: Phenol crotonaldehyde with 15% HEXA (hexamethylenetetramine)
PCR: Phenol crotonaldehyde resorcinol resin
BACKGROUND
The background information hereinbelow relates to the present disclosure but is not necessarily prior art.
Laminates are available in various grades such as industrial laminates and decorative laminates. Industrial laminates are used in various industries, which include electrical transformers, gears, bearing, jigs, fixtures, and thermal breaks, whereas decorative laminates are used in home and office furniture, and the like.
The design of the laminates as per the NEMA (National Electrical Manufacturers Association) or BIS standards (Bureau of Indian Standards) requires the use of phenolic resin, filler or web type material, desired resin content in the prepreg material, and lamination press cycle conditions.
Phenol formaldehyde resins and modified phenolic resins are well known in the preparation of Industrial and Decorative laminates. Phenol is predominantly obtained from fossil fuels, where the prices are not stable and are influenced by various global factors. Generally, formaldehyde at a concentration of 37% with aqueous solutions is being used in resin production. Alternatively, paraformaldehyde produced from the distillation of aqueous solutions (37-50%) of formaldehyde is used for the preparation of phenolic resin.
The recent growth in the demand for the reduction of phenols and aldehydes lead to identifying alternative materials for making phenolic resins. Accordingly, several approaches have been evaluated to substitute or replace with alternative and less expensive chemicals. Phenol was substituted with lignin and other natural phenols in resins. The commercially available lignin’s like lignosulfonates, kraft lignin, and soda lignin were evaluated. Lignin’s due to the high level of polymerization, are not completely soluble in aqueous and or organic solvents. Therefore, the physical and chemical modification of these lignin’s is required to form an active filler in phenolic resin formulation. Lignins that behave as unreactive fillers affect the mechanical performance of the synthesized resin. Further, the use of lignins leads to issues during the impregnation process and affects the properties of the final laminates.
Alternatively, phenol was partially substituted with lignin, and the high-pressure laminates (HPL) were prepared using phenol with lignin, where the self-gluing paper sheets that are soaked with phenol-formaldehyde (PF) resins are stacked in multilayers. The phenol-formaldehyde (PF) resins were unable to penetrate and saturate the paper pores. Partially substituting phenol with bio-based phenolic chemicals like lignin changed the physicochemical properties of the resin and affects its ability to penetrate the paper, thus producing laminate of poor quality.
An Industrial laminate is desired to have very good softness, flexibility, and improved electrical properties. Alternate materials such as CNSL (Cashew Nut Shell Liquid), Nonyl Phenol, Tung oil, and the like were used for preparing phenol formaldehyde resin in a two-stage process wherein firstly phenol is reacted with an acid catalyst at a higher temperature to obtain an adduct followed by adding formaldehyde in the presence of a base catalyst to obtain a resinous product. Similarly, alternatives for formaldehyde like Furfurolaldehyde, Benzaldehyde, cinnamaldehyde, and the like were being evaluated but proved unsuccessful for making phenolic resin-based laminates.
Laminates produced by the alternative materials were unable to provide laminates with the desired softness, and electrical and mechanical properties.
In order to meet the industry requirements, there is an increasing trend to develop phenolic resins from a renewable source. The advantages of using renewable source-based resin can also improve the sustainability of materials.
Therefore, there is felt a need for phenolic polymers from a renewable source that can be used in a laminate and mitigate the drawbacks mentioned hereinabove.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a laminate.
Yet another object of the present disclosure is to provide a laminate that consists of resin from a renewable source.
Another object of the present disclosure is to provide a laminate based on crotonaldehyde.
Still another object of the present disclosure is to provide a simple and efficient process for the preparation of a laminate.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates the impregnation tank and squeeze roller for the preparation of pre-preg;
Figure 2 illustrates the schematic build-up plan of pre-preg for the preparation of a laminate in accordance with an embodiment of the present disclosure;
Figure 3a illustrates the effect of resin tensile strength of laminate based on bleached kraft paper filler;
Figure 3b illustrates the effect of resin tensile modulus of laminate based on bleached kraft paper filler;
Figure 3c illustrates the effect of resin flexural modulus of laminate based on bleached kraft paper filler;
Figure 3f illustrates the effect of resin flexural strength of laminate based on bleached kraft paper filler;
Figure 4 illustrates the stress-strain relationship of laminate;
Figure 5a illustrates the effect of the type of resin on insulation resistance of laminates based on bleached kraft paper filler at 23°C; and
Figure 5b illustrates the effect of the type of resin on the insulation resistance of laminates based on bleached kraft paper filler at 80°C.
SUMMARY
The present disclosure relates to a laminate and a process for its preparation. In an aspect, the laminate comprises at least one resin impregnated reinforced filler material; at least one uncoated reinforced filler material; wherein the resin impregnated reinforced filler material and uncoated reinforced filler material are stacked between at least two PET films to obtain a laminate.
In another aspect, the process for the preparation of the laminate comprises mixing a predetermined amount of resin with at least one fluid medium to obtain a resin solution, dipping a reinforced filler material in resin solution for a first predetermined time period followed by holding vertically for a second predetermined time period to obtain a resinated reinforced filler material. The excess resin on the surface of the resinated reinforced filler material is removed by squeezing to obtain a coated reinforced filler material. The so obtained coated reinforced filler material is dried at a first predetermined temperature for a third predetermined time period to obtain a solvent free coated reinforced filler material. The solvent free coated reinforced filler material is further dried at a second predetermined temperature for a fourth predetermined time period to obtain a resin impregnated reinforced filler material. At least one resin impregnated reinforced filler material and a predetermined number of uncoated reinforced filler materials are pressed to obtain a pre-preg sheet The pre-preg sheets are disposed between at least two PET films and pressed hydraulically at predetermined conditions to obtain a laminate.

DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
Phenol is the key ingredient in the preparation of laminates. Phenol is predominantly obtained from fossil fuels, where the prices are not stable and are influenced by various global factors.
The recent growth in the demand for the reduction of phenols and aldehydes lead to identifying alternative materials for making phenolic resins. Accordingly, several approaches have been evaluated to substitute or replace with alternative and less expensive chemicals. Phenol was substituted with lignin and other natural phenols in resins. The commercially available lignin’s like lignosulfonates, kraft lignin, and soda lignin were evaluated. Lignin’s due to the high level of polymerization, are not completely soluble in aqueous and or organic solvents. Therefore, the physical and chemical modification of these lignin’s is required to form an active filler in phenolic resin formulation. Lignins that behave as unreactive fillers affect the mechanical performance of the synthesized resin. Further, the use of lignins leads to issues during the impregnation process and affects the properties of the final laminates.
Laminates produced by the alternative materials were unable to provide laminates with the desired softness, electrical and mechanical properties.
In order to meet the industry requirements, there is an increasing trend to develop phenolic resins from a renewable source. The advantages of using renewable source-based resin can also improve the sustainability of materials.
The present disclosure provides a laminate that can mitigate the above mentioned problems. The present disclosure further provides a laminate and a process for the preparation of laminate.
In an aspect of the present disclosure, a laminate comprises at least one resin impregnated reinforced filler material; at least one uncoated reinforced filler material; wherein the resin impregnated reinforced filler material and uncoated reinforced filler materials are stacked between at least two PET films to obtain a laminate.
In an embodiment of the present disclosure, the resin is at least one selected from the group consisting of phenol crotonaldehyde resin, phenol crotonaldehyde resin with 15% hexamethylenetetramine (PC3), and phenol crotonaldehyde resorcinol resin (PCR13, PCR18, and PCR27). In an exemplary embodiment of the present disclosure, the resin is phenol crotonaldehyde resin with 15% hexamethylenetetramine (PC3).
The resin composition details are provided below in Table 1
Table 1: Composition of resin
S. No Resin Mole ratio
1 PC3 P:C:NaOH (1:2:0.3)
+ 15% Hexa
2 PCR13 P:C:R:NaOH (0.6:2:0.4:0.3)
3 PCR18 P:C:R:Hexa
(0.8:2:0.2:0.1)
4 PCR27 P:C:R:NH3
(0.6:2.5:0.4:0.3)
wherein P: Phenol; C: Crotonaldehyde; R: Resorcinol
In an embodiment of the present disclosure, the reinforced filler material is at least one selected from the group consisting of bleached kraft paper (BK paper), a cotton fabric cloth, and a glass fabric cloth.
In an embodiment of the present disclosure, the thickness of uncoated reinforced filler material is in the range of 70 GSM to 200 GSM. In an exemplary embodiment, the thickness of uncoated reinforced filler material is 80 GSM.
In an embodiment of the present disclosure, the thickness of resin impregnated reinforced filler material is in the range of 100 GSM to 300 GSM. In an exemplary embodiment of the present disclosure, the resin impregnated reinforced filler material is 140 GSM.
In another aspect of the present disclosure, there is provided a process for the preparation of the laminate.
The process is described in detail.
In a first step, a predetermined amount of resin is mixed with at least one fluid medium to obtain a resin solution.
In an embodiment of the present disclosure, the resin is at least one selected from the group consisting of phenol crotonaldehyde resin, phenol crotonaldehyde resin with 15% hexamethylenetetramine (PC3), and phenol crotonaldehyde resorcinol resin (PCR13, PCR18, and PCR27). In an exemplary embodiment of the present disclosure, the resin is phenol crotonaldehyde resin with 15% hexamethylenetetramine (PC3).
In an embodiment of the present disclosure, a predetermined amount of resin in the resin solution is in the range of 20% to 50% w/v with respect to the total volume of the resin solution and a fluid medium. In an exemplary embodiment, the amount of resin in the resin solution is 30%.
In an embodiment of the present disclosure, the fluid medium is at least one selected from the group consisting of acetone and methanol.
In an embodiment of the present disclosure, the fluid medium is a mixture of fluid medium in the ratio of 1:1 to 1:2. In an exemplary embodiment of the present disclosure, the fluid medium is a mixture of acetone and methanol in a ratio of 1:1.
In an embodiment of the present disclosure, the resin solution is characterized by having
a. a viscosity (at 25°C by Ford cup B4 (DIN 59211)) in the range of 20 to 30 seconds;
b. resin content (solid content by oven drying method at 150°C for 30 minutes) is in the range of 40 to 45%; and
c. gel time (at 170°C by Hot plate method) is in the range of 80 to160 seconds.
In a second step, the reinforced filler material is dipped in the resin solution for a first predetermined time period followed by holding vertically for a second predetermined time period to obtain a resinated reinforced filler material.
In an embodiment of the present disclosure, the first predetermined time period is in the range of 2 minutes to 10 minutes. In an exemplary embodiment of the present disclosure, the first predetermined time period is 3 minutes.
In an embodiment of the present disclosure, the second predetermined time period is in the range of 1 minute to 5 minutes. In an exemplary embodiment of the present disclosure, the first predetermined time period is 2 minutes.
In an embodiment of the present disclosure, the excess resin on the surface of the resinated reinforced filler material is squeezed to obtain a coated reinforced filler material.
In an embodiment of the present disclosure, the squeezing is done by using a squeeze roller or by placing glass rods on both sides and positioned like a squeeze roller.
In a third step, the coated reinforced filler material is dried at a first predetermined temperature for a third predetermined time period to obtain a solvent free coated reinforced filler material.
In an embodiment of the present disclosure, the first predetermined temperature is in the range of 30°C to 40°C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 35°C.
In an embodiment of the present disclosure, the third predetermined time period is in the range of 20 minutes to 40 minutes. In an exemplary embodiment of the present disclosure, the third predetermined time period is 30 minutes.
In an embodiment of the present disclosure, the solvent free coated reinforced filler material is dried at a second predetermined temperature for a fourth predetermined time period to obtain a resin impregnated reinforced filler material.
In an embodiment of the present disclosure, the second predetermined temperature is in the range of 50°C to 170°C.
In an embodiment of the present disclosure, the solvent free coated reinforced filler material is vertically hanged in a hot air circulating oven, the temperature is gradually raised from 60+/-3°C for 10 min, followed by 80+/-3°C for 10 min, further at 120+/-3°C for 5 min and finally at 140+/-3°C for 5 min.
In an embodiment of the present disclosure, at least one resin impregnated reinforced filler material and a predetermined number of uncoated reinforced filler material are pressed to obtain a pre-preg sheet.
In an embodiment of the present disclosure, the predetermined number of uncoated reinforced filler material is in the range of 6 to 12. In an exemplary embodiment of the present disclosure, the predetermined number of uncoated reinforced filler material is 10.
In the final step, a predetermined number of pre-preg sheets are disposed of between at least two PET films and pressed hydraulically at predetermined conditions to obtain a laminate.
In an embodiment of the present disclosure, the thickness of the PET film is in the range of 70 GSM to 90 GSM.
In an embodiment of the present disclosure, predetermined conditions include lamination pressure in the range of 1300 psi to 1500 psi, lamination temperature in the range of 170°C to 190°C for a time period in the range of 20 minutes to 40 minutes, and curing temperature in the range of 175°C to 185°C for a time period in the range of 25 minutes to 35 minutes. In an exemplary embodiment of the present disclosure, the lamination pressure is 1375 psi, cured by gradually increasing the temperature to 185°C over a period of 30 minutes.
The laminates produced according to the present disclosure, are evaluated for tensile strength, tensile modulus, flexural strength, flexural modulus, insulation resistance, and surface resistivity.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment but are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
EXPERIMENTAL DETAILS
Example 1: Preparation of the laminates in accordance with the present disclosure
a) Preparation of a resin solution
300 gm of PC3 with 15% Hexa was mixed with 700 ml of a solvent mixture of acetone and methanol (1:1) slowly under stirring to obtain a resin solution. The viscosity of the resin solution (at temp 25°C by Ford cup B4 (DIN 59211)) is 25 seconds, resin content (solid content by oven drying method at 150°C for 30 minutes) is 40%, and gel time is 120 seconds (at 170°C by hot plate method).
b) Preparation of pre-preg sheets
500 gm of the resin solution was poured into a plastic HDPE tray (size of LxWxD in inches: 24x15x4), followed by dipping bleached kraft paper of 80GSM (8x8) several times into the resin solution for 3 min and holding straight vertically for 2 min to obtain a resinated reinforced filler material. The (excess resin solution on) resinated reinforced filler material was squeezed using glass rods on both sides and positioned like a squeeze roller in the impregnation tank, as illustrated in Fig. 1 and then pressed the rods and squeezed the excess resin from the surface of the impregnated paper to obtain a coated reinforced filler material. The so obtained coated reinforced filler material was hanged vertically at 35°C for 30 min to remove solvents to obtain a solvent free coated reinforced filler material. The solvent free coated reinforced filler material was dried by hanging vertically in a hot air circulating oven and dried at 60°C for 10 min, followed by 80°C for 10 min, further at 120°C for 5 min, and finally at 140°C for 5 min to obtain the PC3 impregnated bleached kraft paper (resin impregnated reinforced filler material).
The thickness of the PC3 impregnated bleached kraft paper is in the range of 140 to 150 GSM.
c) Preparation of the laminate:
10 no’s of bleached kraft paper sheets and 1 PC3 impregnated bleached kraft paper were stacked and pressed to obtain a pre-preg sheet. The pre-preg sheet was placed between PET film of 75 GSM on top and bottom of bleached kraft paper pre-preg sheets pack to get a proper release from the stainless steel plates. Further 6 no’s of 165 GSM unbleached kraft papers on top and bottom of the PET film were placed to give proper cushioning and uniform pressure and temperature to the pre-preg pack. The schematic build-up plan is illustrated in Fig. 2.
The bleached kraft paper pre-preg sheet and PC3 impregnated bleached kraft paper disposed between PET film was laminated at a pressure of 1375 psi, and cured by gradually increasing the temperature to 185°C over a period of 30 minutes. After the cure cycle, the temperature was reduced to below 40°C within 35 minutes to obtain the laminate.
Example 2: Mechanical properties
The mechanical performance of the laminates was studied by comparing tensile strength, a tensile modulus, a flexural strength, and a flexural modulus of laminates prepared by using different resins. For the evaluation of various resins, five specimens (A-E) with different resins are prepared.
Specimen A was prepared by using PC3 resin which was based on NaOH as a catalyst, in addition to this, used 15% HEXA as an accelerator to convert to thermoset behavior. Specimen B was prepared by using PCR13 resin which was prepared by NaOH as a catalyst. Specimen C was based on PCR18 which was synthesized by HEXA as a catalyst. Specimen D was based on PCR27 which was synthesized by using ammonia as a catalyst. Specimen E was based on PF (1:2 mol ratio) and synthesized by using NaOH as a catalyst. The laminate was prepared by using bleached kraft paper as filler. The details of the five types of resins that were used during the lamination process and tested the performance was provided in Table-2.
Table 2: Design of Experiment for Laminate preparation

Laminates (A, B, C, D, E) were produced by impregnating five types of resin as PC3, PCR13, PCR18, PCR27, and PF resins with bleached kraft paper as filler. A total of ten laminates were produced (2 for each resin).
The tensile testing was performed to determine the tensile strength and tensile modulus which was carried out according to ASTM D638–08 method by using a universal testing machine for tensile properties used for plastics material. The static tensile tests and Flexural tests according to ASTM-D790 were conducted in the laboratory where the temperature was maintained at 23°C and 50% relative humidity.
One way ANOVA method was used to study the effect of resin on mechanical properties such as tensile strength, tensile modulus, flexural strength, and flexural modulus.
The mechanical properties i.e. tensile strength, tensile modulus, flexural strength, and flexural modulus of laminates (PC3, PCR13, PCR18, PCR27, and PF resin) of laminates are provided below in Table 3.
Table 3: Mechanical properties of laminates
Resin Type Tensile Strength (Mpa) Tensile Modulus (Mpa) Flexural Strength (Mpa) Flexural Modulus (Mpa)
PC3 72 5200 136.5 7000
PCR13 101 5450 160.5 8259
PCR18 80 7800 158 8200
PCR27 139 8200 216 10700
PF3 63 6200 166 8305
In the ANOVA (Table 3 (a) and (b)), the P-Value of the type of resin for tensile strength is 0.003 and for flexural strength is 0.040 value which indicates that there is sufficient evidence that not all the means are equal when alpha is set at 0.05. The interval plot displays the mean and confidence interval for each group. The high R-sq values of 94.09% for tensile strength and 82.43% for flexural strength of PC3 resin are provided in Table 3a) and 3b).
Table 3a): Analysis of Variance for the type of resin (PC3) for tensile strength
Table 3b): Analysis of Variance for the type of resin (PC3) for Flexural Strength
DF: Degrees of freedom
Adj SS: Adjusted sum of squares
Adj Ms: Adjusted mean squares
F-Value: the ratio of two mean square values
P-Value: the probability of obtaining the observed results
S: the standard deviation
R-sq: Coefficient of determination and it determines the proportion of variance in the dependent variable that can be explained by the independent variable.
The mechanical properties of laminates prepared using a bleached kraft paper as a reinforced media for different resins as described in Fig. 3a-d laminates based on PC3, PCR13, PCR18, PCR27, and PF resins have highlighted changes in the mechanical properties. The results for the tensile strength, tensile modulus, flexural strength, and flexural modulus, are illustrated in Fig. 3a-d.
It is observed that the tensile strength and the flexural strength have the same incremental trend and flexural strength is almost 1.5 times more than the tensile strength. The tensile modulus and the flexural modulus have the same incremental trend for all type of resins except for PCR18. The flexural modulus is tentatively 1.4 times more than that of the tensile modulus. The tensile modulus is almost 1.6 times more than that of the tensile strength except for PCR18. The flexural strength and the flexural modulus have the same incremental trend for different resins and the magnitude of the flexural modulus is around 50 to 60 times more than that of the flexural strength.
It was observed that the laminate based on PCR27 resin was found to be tougher than all other laminates. PC3 resin based laminate was more elastic than PCR13 resin base laminate. As compared to PCR13 modified resin, PF resin provided lesser interaction with pores matrix of the paper surface, whereas, PCR-13 resin has higher cross-linking of resorcinol that might provide a higher side of interaction with paper surface. Moreover, the reason for the more elastic behavior of PC3 resin-based laminate is anticipated due to the linear chain-like novolac type thermoplastic nature, and Hexa helped to convert thermoset behavior.
The PC3 system was found to be more elastic as predicted due to the presence of double bonds in the crotonaldehyde in the polymer matrix. PCR 27, the ammonia-based catalyst system exhibited tougher plastic nature and is found to be comparable with the conventional ammonia-based PF resol system. The PCR-13 resin shows an almost equal tensile property with the conventional PF resin. Also, the laminates developed from PC and PCR base resin showed an impact on the toughness of the laminate as compared to the laminate based on conventional PF resin. Therefore, the properties of PC3, PCR-13, and PF resin influenced the mechanical performance of the laminate.
Example 3: Stress-strain relationship
The tensile stress of laminate can be calculated by dividing the load value by the cross-sectional area of the sample. The strain of laminate can be collected by the strain gauge system. The relationship curves of the five types of laminates are illustrated in Fig. 4. From this figure, it is observed that, in the first stage, fibers and resins are working together to absorb the tensile load. Cracking or debonding is not seen. The strain increased slower than stress, and the first stage of the curve is formed. When the initial cracks are observed that are attributed to some resins ruptured and debonding between fibers and resins takes place. The increase in the deformation of specimens was observed more quickly than the loads, and thus the second stage of the curve was formed. When the cracks increased, more and more resins ruptured, and the loads were mainly absorbed by fibers until reaching the bearing capacity and the ultimate stress of specimens was reached.
The laminates prepared by resin PCR27 showed more toughness as compared to the laminates prepared by conventional PF resin and other PC/PCR resin which were synthesized by NaOH and Hexa as a catalyst. Moreover, the laminate prepared by resin PCR13 showed comparatively similar mechanical performance as the laminate based on PF resin.
Example 4: Effect of the resin on the physical and electrical properties of the laminates
The physical properties of the laminates were evaluated by density and water absorption, whereas the electric properties are evaluated by
1. Insulation resistance of sample immersed in water for 24 h at a 23°C;
2. Insulation resistance of above-immersed sample in water for 24 h at 23°C and then dried at 80°C for 60 min in the air circulating oven.
The insulation resistance was measured by using an insulation tester, the results are illustrated in Figures 5a and 5b.
One-way ANOVA was conducted separately for all laminates based on five different resins and with BK paper substrates for the insulation resistance. In the ANOVA table (Table 4), the 0.00 P-Value for the type of resin indicates that there is sufficient evidence that not all the means are equal when alpha is set at 0.05 means type of resin influences the properties of laminates. The interval plot (Fig. 5a and 5b) displays the mean and confidence interval for each group. The high predicted R2 (95.01%) suggests that the model will predict new observations nearly as well as it fits the sample data.

Table 4: Analysis of variance for absorption

The insulation resistance of laminates prepared using a bleached kraft paper filler material for different resins at 23°C and 80°C were described in Figures 5a and 5b. Laminates based on PC, PCR, and PF resins synthesized by using different catalyst has an impact on the insulation resistance of laminate. Insulation resistance (MO) -D24/23 (Insulation resistance of sample immersed in water for 24 h at a temperature of 23°C) was highest for laminate based on PCR27 and lowest for the laminate based on PF3 resin. Overall, PC and PCR laminates were having higher insulation resistance than PF resin as shown in Figures 5a and 5b.
The insulation resistance (IR) of electrical properties of the laminate based on different resins is provided below.
Table 5: Electrical properties of the laminate
It is evident from the above data that the insulation resistance (MO) - E1/105a is increased in the case of all laminate because of loss of water. Insulation resistance (MO) - E1/105a was very high in laminates prepared from PC27 compared to other laminates. It is the lowest for laminates based on PF resin. This proves that laminates based on all PC and PCR resin show far better insulation resistance properties as compared to PF resin.
Further, the surface resistivity was evaluated by four-probe methods by using the modern instrument ‘KEITHLEY SCS-4200 at CEMET PUNE LAB. The results are provided below,
Table 6: Surface resistivity of the laminate
Type of Resin Catalyst used Type of Filler D24/23 /MO
PC3 (15% Hexa) NaOH Bleached Kraft Paper 1179.85
PCR13 NaOH & Resorcinol Bleached Kraft Paper 1022.22
PCR18 Hexa & Resorcinol Bleached Kraft Paper 1137.43
PCR27 Ammonia & resorcinol Bleached Kraft Paper 1631.50
PF3 NaOH Bleached Kraft Paper 417.51
It is evident from the above data that the surface resistivity results are also indicative that PC resins are superior in electrical properties as compared to the conventional PF systems and also PCR27 for the higher electrical property. The resin for this higher electrical behavior is attributed due to the presence of double bonds in crotonaldehyde contributed to the higher electrical properties like conventional alkyd systems.
Example 5: Water absorption
The water absorption results for PC3/PCR13/PCR18/PCR27/PF Resin system laminates made using BK Paper, Cotton Fabric Cloth, and Glass Fabric Cloth as a reinforced filler material are evaluated using ASTM-D570. The results are provided below in Table-7.
Table 7: Water absorption of the laminate

It is evident from the above data that the laminates prepared by using glass fabric cloth have less water absorption when compared to other reinforced filler materials. Further, PCR27 provides better water absorption properties with reinforced filler materials in comparison with other resin materials.
Example 6: Mechanical properties
The mechanical properties i.e. tensile strength, tensile modulus, flexural strength, and flexural modulus of laminates (PC3, PCR27, and PF resin) based on different reinforced fillers (BK Paper, Cotton Fabric Cloth, and Glass Fabric Cloth) as a reinforced web material were evaluated. The results are provided below in Table-8, 9, 10 and 11.
Table 8: Tensile strength of laminates based on glass fabric, cotton fabric, and B.K. paper

Table-9: Tensile modulus of laminates based on glass fabric, cotton fabric, and B.K. paper

It is evident from the above data that PCR27 resin system along with the glass fabric reinforced filler material has the highest tensile strength and tensile modulus. Further, the laminates made by using the glass fabric reinforced filler material have better tensile strength and tensile modulus in comparison to other filler materials such as cotton fabric and bleached kraft paper.
Table 10: Flexural strength of laminates based on glass fabric, cotton fabric, and B.K. paper

Table 11: Flexural modulus of laminates based on glass fabric, cotton fabric, and B.K. paper

It is evident from the above data that PC3 resin system along with the glass fabric reinforced filler material has highest flexural strength and flexural modulus. Further, the laminates made by using glass fabric reinforced filler material have better flexural strength and flexural modulus in comparison to other filler materials such as cotton fabric and bleached kraft paper.
Example 7: Surface Resistivity
The surface resistivity for PC3/PCR13/PCR18/PCR27/PF Resin system laminates made using BK Paper, Cotton Fabric Cloth, and Glass Fabric Cloth as a reinforced web material were evaluated using KEITHLEY SCS-4200 (Four Probe measurement method). The results are provided below in Table-12.
Table 12: Surface resistivity of laminates based on glass fabric, cotton fabric, and B.K. paper

It is evident from the above data that PCR27 resin system with bleached kraft paper reinforced filler material has the highest surface resistivity. Further, the laminates made by using bleached kraft paper reinforced filler material have better surface resistivity in comparison to other filler materials such as cotton fabric and glass fabric.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a laminate that:
• has enhanced mechanical and physical strength;
• the presence of double bonds (unsaturated) in the polymeric resins produces laminates with increased softness, improved electrical properties, and insulation resistance;
• uses molasses to extract crotonaldehyde;
• uses waste material, thus reducing environmental pollution;
• use of crotonaldehyde in phenolic resins reduces waste generation; and
• cost-efficient, since the crotonaldehyde is synthesized from molasses, bye product produced in the sugar industry.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step,” or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM
1. A laminate comprising
a. at least one resin impregnated reinforced filler material;
b. at least one uncoated reinforced filler material;
wherein said resin impregnated reinforced filler material and uncoated reinforced filler material is stacked between at least two PET films to obtain a laminate.
2. The laminate as claimed in claim 1, wherein said resin is at least one selected from the group consisting of phenol crotonaldehyde resin, phenol crotonaldehyde resin with 15% hexamethylenetetramine (PC3), and phenol crotonaldehyde resorcinol resin (PCR13, PCR18, and PCR27).
3. The laminate as claimed in claim 1, wherein said reinforced filler material is at least one selected from the group consisting of bleached kraft paper, a cotton fabric cloth, and a glass fabric cloth.
4. The laminate as claimed in claim 1, wherein the thickness of said uncoated reinforced filler material is in the range of 70 GSM to 200 GSM.
5. The laminate as claimed in claim 1, wherein the thickness of said resin impregnated reinforced filler material is in the range of 100 GSM to 300 GSM.
6. A process for the preparation of laminate as claimed in claim 1, wherein said process comprising the following steps:
a. mixing a predetermined amount of resin with at least one fluid medium to obtain a resin solution;
b. dipping a reinforced filler material in resin solution for a first predetermined time period followed by holding vertically for a second predetermined time period to obtain a resinated reinforced filler material;
c. squeezing said resinated reinforced filler material to remove excess resin present on a surface of resinated reinforced filler material to obtain a coated reinforced filler material;
d. drying said coated reinforced filler material at a first predetermined temperature for a third predetermined time period to obtain a solvent free coated reinforced filler material;
e. drying said solvent free coated reinforced filler material at a second predetermined temperature for a fourth predetermined time period to obtain a resin impregnated reinforced filler material;
f. pressing at least one resin impregnated reinforced filler material and a predetermined number of uncoated reinforced filler material to obtain a pre-preg sheet;
g. disposing said pre-preg sheets between at least two PET films and pressing hydraulically at predetermined conditions to obtain a laminate.
7. The process as claimed in claim 6, wherein said predetermined amount of resin in the resin solution is in the range of 20% to 50% w/v with respect to total volume of the resin solution and a fluid medium.
8. The process as claimed in claim 6, wherein said fluid medium is at least one selected from acetone and methanol.
9. The process as claimed in claim 6, wherein said fluid medium is a mixture of acetone and methanol having a ratio in the range of 1:1 to 1:2.
10. The process as claimed in claim 6, wherein said resin solution is characterized by having
a. a viscosity (at 25°C by Ford cup B4 (DIN 59211)) is in the range of 20 to 30 seconds;
b. resin content (solid content by oven drying method at 150°C for 30 minutes) is in the range of 40 to 45%; and
c. gel time (at 170°C by Hot plate method) is in the range of 80 to 160 seconds.
11. The process as claimed in claim 6, wherein said first predetermined time period is in the range of 2 minutes to 10 minutes; second predetermined time period is in the range of 1 minute to 5 minutes; third predetermined time period is in the range of 20 minutes to 40 minutes and fourth predetermined time period is in the range of 10 minutes to 30 minutes.
12. The process as claimed in claim 6, wherein said first predetermined temperature is in the range of 30°C to 40°C and second predetermined temperature is in the range of 50°C to 170°C.
13. The process as claimed in claim 6, wherein said predetermined number of uncoated reinforced filler material is in the range of 6 to 12.
14. The process as claimed in claim 6, wherein said predetermined conditions include lamination pressure in the range of 1300 psi to 1500 psi, lamination temperature in the range of 170°C to 190°C for a time period in the range of 20 minutes to 40 minutes, and curing temperature in the range of 175°C to 185°C for a time period in the range of 25 minutes to 35 minutes.
Dated this 24th day of August, 2022

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI