DESC:FIELD OF THE INVENTION:

The present invention covers a novel modified cellulose and process for preparation thereof. The modified cellulose acting as a nucleating agent in polypropylene matrix.

BACKGROUND OF THE INVENTION:

Polypropylene is known to have three crystalline phases, a, ß and ? phases besides amorphous phase. Polypropylene crystallizes to a form (monoclinic) which is the most thermodynamically stable form. Polypropylene, however, may also crystallize in the ß-form (hexagonal) and in ?-form (orthorhombic).

Nucleating agents as one of the additives presents a role of increasing the nucleation density of polymer greatly and enhancing the nucleation rate dramatically. The rate of crystallization and the size of the crystals have a strong impact on the mechanical and optical properties after conversion of the plastic, especially (but not exclusive) in polypropylene. The addition of nucleating agents to the semi-crystalline polymers like polypropylene provides a surface on which the crystal growth can start. As a consequence, fast crystal formation will result in many small crystal domains and will increase the crystallization temperatures tremendously. Due to this phenomenon, cycle time in injection molding processes is reduced and mechanical properties like flexural modulus, strength, heat distortion temperature and hardness is increased.

Quillin et al. (Journal of Applied Polymer Science, Vol. 50,1187-1194 (1993)) studies reported effect of various chemical surface treatments on the nucleation ability of cellulose in Polypropylene. Chemicals used in the study were alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), and stearic acid. Results showed decrease in crystallinity and increase in melting temperature of Polypropylene.

P. Bataille et al. (Polymer composites, April 1989, Vol. 10, No. 2) reports a systematic study of the effect of surface pretreatment of cellulosic fibers and the processing time and temperature on the mechanical properties of the cellulose containing polypropylene. y-metacryloxy-propyltrimethoxysilane (A-174) and y-amino-propyltriethoxysilane (A- 1 100) are the two silane coupling agents used in this work. Strong adhesion with silane treated fiber promoted delamination of the cellulose fibers. The presence of maleic anhydride modified polypropylene improves the adhesion and aids the dispersion of the cellulosic fibers in the matrix.

In an another published research journal paper; S. Spoljaric et al.(Composites: Part A 40 (2009) 791–799) prepared and characterized PP–microcrystalline cellulose (MCC) composites, through modification of fiber surface and the addition of PP-g-MA as a compatibilising agent. For surface treatment of fiber, fatty acid, a silane coupling agent and an alkyl titanate were used. Microcrystalline cellulose was varied from 1% to 10%. Cellulose increased crystallization temperature of composite. Peak crystallization temperature (Tc) of composite (10% cellulose loading) increased to 123°C from 115°C of neat PP.

US2010317779 discloses a composition of scratch resistant polypropylene with a nucleating agent selected from the group consisting of sodium benzoate, 2,2’-methylene-bis(4,6-di-tert-butylphenyl)phosphate, zinc glycerolate, calcium salt of 1,2-dicarboxylic acid cyclohexane and sodium salt of 1,2-dicarboxylic acid norbornane.

US2010010168 and WO2011131123 describe the use of carboxylate compounds as nucleating agents, the latter in combination with a phosphate type nucleating agent.

US201113101330 discloses a polypropylene resin composition compromising an polypropylene polyethylene copolymer and an amide compound as nucleating agent.

EP0557721 and EP1431335 describe bisamide compounds compounds for the crystallization of polypropylene. Dibenzyllidene sorbitol compounds are common nucleator compounds particularly for polypropylene end products. Compounds such as 1,3-0-2,4-bis(3,4-dimethyl-benzylidene) sorbitol (herein after DMDBS), available from Milliken chemical under the trade name Millard 3988, provide excellent nucleation characteristics for the target PP and other polyolefin’s. Other well known compounds include sodium benzoate, sodium 2,2’-methylene-bis-(4,6-di-tert-butylphenyl) phosphate (from Asahi Denka Kogyo K.K., known as NA-11), talc, and the like.

Other acetals of sorbitol and xylitol are typical nucleators for polyolefin’s and other thermoplastics as well. US4016118 discloses Dibenzyllidene sorbitol (DBS) as an effective nucleating and clarifying agent for Polyolefin’s. Since then large number of acetals of sorbitol and xylitol have been disclosed. Representative US patents include Pat No. 4314039 on di(alkylbenzylidene) sorbitols; Mhaffey, Jr., US Pat No. 4371645 on di-acetals of sorbitol having at least one chlorine or bromine substituent; Koayashi, et. al., US Pat no. 4532280 on di(methyl or ethyl substituted benzylidene) sorbitol; Rekers, US Pat No. 5049605 on bis(3,4-dialkaylbenzylidene) sorbitols including substituent forming a carbocyclic ring.

US Pat No. 3207735, 3207736 and 3207738 discloses effective nucleating agents based on metal salts of organic acids. US Pat No. 3207737 and 3207739 suggests that aliphatic, cycloaliphatic and aromatic carboxylic, dicarboxylic or higher polycarboxylic acids, corresponding anhydrides and metal salts are effective nucleating agents for polyolefin’s. They further state that benzoic acid type compounds in particular sodium benzoate are the best embodiment of the nucleating agents.

Another class of nucleating agents in US Pat No 4463113 were disclosed which were based upon cylic bis phenol phosphates compounds. Kimura, et. al. suggested in US Pat No. 5342868 that the addition of an alkali metal carboxylate to basic polyvalent metal salt of cyclic organophosphoric ester can further improve the clarification effects of such additives. Compounds that are based upon these technologies are marketed under trade name of NA-11 and NA-21.

SUMMARY OF THE INVENTION:
According to one embodiment of the present invention a process for modification of cellulose comprising the step of treating cellulose with a dibasic acid or a mixture of dibasic acids at room temperature to obtain modified cellulose.
According to another embodiment modified cellulose of the present invention acts as a nucleating agent for polypropylene.
According to another embodiment of the present invention a process of nucleation of polypropylene matrix comprising of treating the polypropylene matrix with the modified cellulose.

According to the present invention modified cellulose of the present invention can be used as effective nucleating agent for polypropylene. The present invention has the following advantages over the prior arts:

• Higher crystallization temperature of polypropylene achieved when nucleated with modified cellulose of the present invention.
• Use of modified cellulose in ppm levels.
• Lower starting material cost and no complicated synthesis steps involved.
• No high temperature or pressure or sophisticated equipments or purification steps required.
• No compatibility issues with other additives used in polypropylene e.g. acid scavengers, antioxidants etc.
• No specialty chemicals like coupling agents etc. required for enhancement in mechanical properties of polypropylene.
• Polypropylene nucleated with modified cellulose has improved properties over non nucleated polypropylene.
• Enhancement in physio-mechanical properties of polypropylene, especially flexural modulus and crystallization temperature.

OBJECTIVE OF THE INVENTION:

The object of the present invention is to provide a novel and economical process for modification of cellulose for its use as a nucleating agent in polypropylene matrix.

It is further objective of the invention that cellulose can be effectively modified to be used as efficient nucleating agent in polypropylene without involving much complicated synthesis steps.

It is further objective of the present invention is to provide process involves treating a mixture comprising of organic dibasic acid in organic solvent with cellulose and the modified cellulose when used in polypropylene matrix gives enhancement in properties.

Various objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention.

DESCRIPTION OF THE INVENTION:

While the invention is susceptible to various modifications and/or alternative processes and/or compositions, specific embodiment thereof has been shown by way of example in tables and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular processes and/or compositions disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the invention as defined by the appended claims.

The tables and protocols have been represented where appropriate by conventional representations, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

The following description is of exemplary embodiments only and is not intended to limit the scope, applicability or configuration of the invention in any way. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Various changes to the described embodiments may be made in the function and arrangement of the elements described without departing from the scope of the invention.
Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to many thousands of ß(1?4) linked D-glucose units. The present invention intends to provide effective alpha nucleating agent which does not employ a high temperature for treatment or expensive solvents or purification steps and shows good enhancement in properties of polypropylene.
According to one embodiment of the present invention a process for modification of cellulose comprising the step of treating cellulose with a dibasic acid or a mixture of dibasic acids at room temperature to obtain modified cellulose.
According to preferred embodiment of the present invention the dibasic acid is selected from dibasic organic acids comprising four or more carbon atoms.
According to preferred embodiment of the present invention the dibasic acid is selected from pimelic acid, suberic acid, azelaic acid, o-phthalic acid, terephthalic acid or a combination thereof.
According to preferred embodiment of the present invention the dibasic acid is pre-mixed with an organic solvent.
According to preferred embodiment of the present invention the premixing of the dibasic acid in an organic solvent is carried out at a temperature between 10ºC to 40ºC or the temperature not exceeding beyond the boiling point of the organic solvent.
According to preferred embodiment of the present invention the premixing is carried out for duration of 30 minutes or longer or 1 hour or longer, more preferably 1.5 hours or longer.
According to preferred embodiment of the present invention the premixing is carried out at ambient pressure, either in presence of air or in presence of inert gas, such as nitrogen.
According to preferred embodiment of the present invention the process further comprising of subjecting the modified cellulose to a drying process to remove the organic solvent.
According to preferred embodiment of the present invention the process further comprising of comprising of cooling the modified cellulose at room temperature and optionally milling it to fine powder with an average particle size of 1-10 µm.
According to another embodiment modified cellulose of the present invention acts as a nucleating agent for polypropylene.
According to another embodiment of the present invention a process of nucleation of polypropylene matrix comprising of treating the polypropylene matrix with the modified cellulose of the present invention.
According to preferred embodiment of the present invention the modified cellulose acting as a nucleating agent is added in the polypropylene matrix in amount from 0.001 to 5 wt.%, or 0.01 wt.% to 5 wt.% on the basis of the polypropylene content.
According to preferred embodiment of the present invention the polypropylene is a homopolymer, impact copolymer, random copolymers or block copolymers.

The present invention is directed to the preparation of a novel nucleating agent by treating cellulose with a mixture comprising of organic dibasic acid and organic solvent or alone dibasic acid.

The dibasic in accordance with present invention may be selected among dibasic organic acids comprising four of more carbon atoms. Preferred examples of the dibasic acids are pimelic acids, suberic acids, azelaic acids, o-phthalic acids, terephthalic acid acid etc. These acids can be used as alone or in any desired admixture. Preferred are pimelic acid and suberic acid. The dibasic organic acid may be used in any desired ratio, suitable do mixtures comprise higher or equal amount to the cellulose.

In accordance with the present invention, organic dibasic acid can be admixed as such with the cellulose or it can be first dissolved in an organic solvent. Premixing of the dibasic acid in an organic solvent may be carried out preferably at temperature between 10 to 40 0C or temperature should not exceed beyond the boiling point of the organic solvent. Time for premixing is 30 minutes or longer, more preferably 1 hour or longer, and in particular 1.5 hours or longer, such as about 2 hours. The premixing is carried out at ambient pressure, either in presence of air or in presence of inert gas, such as nitrogen.

In accordance with process of the present invention, treatment may be carried out in any desired and suitable device, including stirred vessels as well as fluidized bed reactors. These devices, which are well known to the skilled person, enable an efficient premixing or treatment. After treatment, the obtained compound or nucleating agent may be further subjected to post treatments, in particular after having been cooled down to room temperature. In case solvent used for premixing dibasic acid, vacuum oven or hot air oven may be used. Time for vacuum drying or hot air drying may be 30 minutes or longer, more preferably 4 hour or longer, and in particular 6 hours or longer, such as about 8 hours. Drying is carried out at ambient pressure, either in presence of air or in presence of inert gas, such as nitrogen.

It is preferred to subject the dried powder to further milling treatment to obtain a fine powder having a weight average particle size of from 1 to 10 µm, preferably 2 to 7 µm and in particular 3 to 6 µm.

The compound or nucleating agent obtained in accordance with the present invention may be used in particular form, preferably as fine powder when adding to polypropylene to be nucleated. The nucleating agent thus obtained may be used as fine powder or in form of master batch, use as fine powder is preferred. The nucleating agent thus obtained by the present invention is used in polypropylene matrix in amounts of from .001 to 5 wt.%, preferably .01 wt.% to 3 wt.% such as from .1% to 1 wt.% (calculated on the basis of the polypropylene content).

The polypropylene to which the a-nucleating agent in accordance with the present invention may be added may be a homopolymer as well as a impact copolymer, including random copolymers as well as block copolymers. The polypropylenes are typically stereoregular polypropylenes, such as isotactic polypropylenes as well as elastomeric polypropylenes having a degree of stereo regularity of preferably 80% or more. Stereo regularity is preferably determined by 13C-NMR spectroscopy in solution as described e.g. by Busico et al. in Macromolecules 28 (1995) 1887-1892, taking the isotactic pentad regularity as measure of stereoregularity.

It will be appreciated that several of the details set forth below examples are provided to describe the following embodiments in a manner sufficient to enable a person skilled in the relevant art to make and use the disclosed embodiments.

EXAMPLES:

In mixtures 2-6, novel nucleating agent (modified cellulose) are used in homo polypropylene (Homo-PP) matrix (3MFI). Novel nucleating agent is varied from 250ppm to 2000ppm.

Similarly five mixtures, 7-11 are prepared using homo polypropylene (3MFI) with sodium benzoate (NaBz). Sodium benzoate is varied from 250ppm to 2000ppm. Results from PP nucleated with sodium benzoate are used as reference.

Novel nucleating agent prepared by treating cellulose with organic dibasic acids premixed in organic solvent at room temperatures for 4 hours, then putting the mixtures into a vacuum oven at 500C for 2 hours. After cooling to room temperature all mixtures are milled to a fine powder with an average particle size of 3-10 µm.

Table 1: Recipe for modification of Cellulose
S.No. Cellulose
(grams) Dibasic acid
(grams) Comment Treatment
(0C)
1 10 10 wt. by wt. 4h/25 0C

Example 1: Mixtures (S.No. 1-11) are evaluated for homo-PP nucleated with novel nucleating agent and sodium benzoate.
S.No. Polypropylene
Modified Cellulose
(ppm) Sodium Benzoate
(ppm)
1 Neat PP - -
2 250 ppm -
3 500 ppm -
4 1000 ppm -
5 1500 ppm -
6 2000 ppm -
7 - 250 ppm
8 - 500 ppm
9 - 1000 ppm
10 - 1500 ppm
11 - 2000 ppm

Example 2: Mixtures (S.No. 12-17) are evaluated for Impact Copolymer – Polypropylene (ICP-PP) (3 MFI) nucleated with novel nucleating agent
S.No. Polypropylene
Modified Cellulose
(ppm)
12 Neat PP -
13 250 ppm
14 500 ppm
15 1000 ppm
16 1500 ppm
17 2000 ppm

Examples 3:- Mixtures (S.No. 18-20) are evaluated for Polypropylene-Random Copolymer (PP-RCP) (12 MFI) nucleated with novel nucleating agent

S.No. Polypropylene
Modified Cellulose
(ppm)
18 Neat PP -
19 1000 ppm
20 2000 ppm

Examples 4:- Mixtures (S.No. 21-26) are evaluated for Homo-Polypropylene (11 MFI) nucleated with novel nucleating agent
S.No. Polypropylene
Modified Cellulose
(ppm)
21 Neat PP -
22 250ppm
23 500ppm
24 1000 ppm
25 2000 ppm
26 1%

Recipes and results:
1) Homo-PP and modified cellulose

Mixture of polypropylene homopolymer (Homo-PP) (MFR (2300C/2.16 Kg): 3g/10min and 11g/10min) and modified cellulose as mentioned above (mixtures 2-6 and 22-26) are prepared and stabilized/mixed with 0.35% pentaerthrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)-propionate) (supplied as Irganox 1010, Ciba SC), 0.70% tris(2,4-ditert-butyl-phenyl) phosphite (supplied as Irgafos 168, Ciba SC) and 0.375% calcium stearate.

2) Homo-PP and Sodium benzoate

Mixture of polypropylene homopolymer (Homo-PP) (MFR (2300C/2.16 Kg): 3g/10min) and sodium benzoate as mentioned above are prepared (mixtures 7-11) and stabilized/mixed with 0.35% pentaerthrityl-tetrakis(3-(3’,5’-di-tert--butyl-4-hydroxyphenyl)-propionate) (supplied as Irganox 1010, Ciba SC), 0.70% tris(2,4-ditert-butyl-phenyl) phosphite (supplied as Irgafos 168, Ciba SC) and 0.375% calcium stearate.

3) Polypropylene Impact copolymer (PP-ICP) and modified cellulose

Mixture of impact copolymer (ICP-PP) powder (MFR (2300C/2.16 Kg): 3g/10min) and modified cellulose as mentioned above are prepared (mixtures 13-17) and stabilized/mixed with 0.35% pentaerthrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)-propionate (supplied as Irganox 1010, Ciba SC), 0.70% tris(2,4-ditert-butyl-phenyl) phosphite (supplied as Irgafos 168, Ciba SC) and 0.375% (calcium stearate).

4) Polypropylene Random copolymer (PP-RCP) and modified cellulose

Mixture of random copolymer (PP-RCP) powder (MFR (2300C/2.16 Kg): 12g/10min) and modified cellulose as mentioned above are prepared (mixtures 19-20) and stabilized/mixed with 0.35% pentaerthrityl-tetrakis(3-(3’,5’-di-tert-butyl-4-hydroxyphenyl)-propionate) (supplied as Irganox 1010, Ciba SC), 0.70% tris(2,4-ditert-butyl-phenyl) phosphite (supplied as Irgafos 168, Ciba SC) and 0.375% calcium stearate).

Mixtures 1 to 26 as mentioned above are extruded at 2300C. The obtained products are evaluated for their crystallization temperatures and the results are shown in the following Table:
S.No Formulations
(Amount of nucleating Agent) Homo-PP & Sodium benzoate
3 MFI
(0C) Homo-PP &
Modified Cellulose
3 MFI
(0C) ICP-PP &
Modified Cellulose
3 MFI
(0C) ICP-RCP &
Modified Cellulose
12 MFI
(0C)
Homo-PP &
Modified Cellulose
11 MFI
(0C)

1 Neat 115 115 113.8 104 116.1
2 250ppm 117.9 120 113.9 - 121.9
3 500ppm 119.6 123.1 121.8 - 122.2
4 1000 ppm 120.9 128.8 128.2 111 126.5
5 1500ppm 123.9 130.4 128.9 - -
6 2000ppm 123.8 130.9 129.8 113 127.9
7 1% - - - - 132.2

Table 1: Showing crystallization temperature of PP nucleated with novel nucleating agent and Sodium benzoate.

From the inventive examples of the present invention it can be clearly seen that with use of novel nucleating agent (modified cellulose), crystallization temperature of homo PP-homopolymer (3MFI) increased from 1150C (neat PP) to 123.80C (at 2000 ppm loading of novel nucleating agent); PP-homopolymer (11MFI) from 116.10C (neat PP) to 132.20C (at 1% loading of novel nucleating agent); for Impact grade Polypropylene (PP-ICP) crystallization temperature increased from 113.80C (neat PP) to 129.80C (at 2000 ppm loading of novel nucleating agent); for random copolymer (PP-RCP) crystallization temperature increased from 1040C to 1110C (1000 ppm loading of novel nucleating agent) and 1130C (2000 ppm loading of novel nucleating agent).

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained and / or the precision of an instrument for measuring the value. Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality.
,CLAIMS:We Claim:
1. A process for modification of cellulose comprising the step of treating cellulose with a dibasic acid or a mixture of dibasic acids at room temperature to obtain modified cellulose.
2. The process of claim 1, wherein the dibasic acid is selected from dibasic organic acids comprising four or more carbon atoms.
3. The process of any of the preceding claims 1-2, wherein the dibasic acid is selected from pimelic acid, suberic acid, azelaic acid, o-phthalic acid, terephthalic acid or a combination thereof.
4. The process of any of the preceding claims 1-3, wherein the dibasic acid is pre-mixed with an organic solvent.
5. The process of claim 4, wherein the premixing of the dibasic acid in an organic solvent is carried out at a temperature between 10ºC to 40ºC or the temperature not exceeding beyond the boiling point of the organic solvent.
6. The process of any of the preceding claims 4-5, wherein the premixing is carried out for duration of 30 minutes or longer, preferably 1 hour or longer, more preferably 1.5 hours or longer.
7. The process of any of the preceding claims 4-6, wherein the premixing is carried out at ambient pressure, either in presence of air or in presence of inert gas, such as nitrogen.
8. The process of any of the preceding claims 4-7, further comprising of subjecting the modified cellulose to a drying process to remove the organic solvent.
9. The process of any of the preceding claims 1-8, further comprising of cooling the modified cellulose at room temperature and optionally milling it to fine powder with an average particle size of 1-10 µm.
10. A modified cellulose as obtained by any of the preceding claims 1-9.
11. The modified cellulose of claim 10 whenever used as a nucleating agent for polypropylene.
12. A process of nucleation of polypropylene matrix, the process comprising of treating the polypropylene matrix with the modified cellulose as claimed in any of the preceding claims 10-11.
13. The process of claim 12, wherein the modified cellulose acting as a nucleating agent is added in the polypropylene matrix in amount from 0.001 to 5 wt.%, or 0.01 wt.% to 5 wt.% on the basis of the polypropylene content.
14. The process of any of the preceding claims 12-13, wherein the polypropylene is a homopolymer, impact copolymer, random copolymers or block copolymers.