CLIAMS:1. A densified thermal bonded polyester block comprising :
a. 30 to 40% by weight of low melt fibers; and
b. conventional staple fibers ,
wherein said densified thermal bonded polyester block is characterized by
• tear strength ranging from 4-7kg/cm;
• tensile strength ranging from 5-8 kg/cm2;
• break elongation property ranging from 115-130%; and
• density ranging from 58-63kg/m3.

2. The densified thermal bonded polyester block as claimed in claim 1, wherein said low melt fibers are polyester low melt fibers.

3. The densified thermal bonded polyester block as claimed in claim 1, wherein said conventional staple fibers are polyester staple fibers.

4. The densified thermal bonded polyester block as claimed in claim 1, wherein the amount of said conventional staple fibers ranges from 60 to 70% by weight of the polyester block.

5. A process for preparing densified thermal bonded polyester block, said process comprising the following steps:
a) mixing 30 to 40% by weight of low melt fibers and conventional staple fibers to obtain a fiber blend;
b) feeding said fiber blend into a conveyor line of a bale opener to obtain a carded web;
c) cross lapping said carded web in a cross lapper to obtain a compressed web;
d) feeding said compressed web in an oven through a conveyor line and passing hot flue gases into said compressed web through multiple channels, for a time period ranging from 10-20 minutes to obtain heated compressed web, wherein the oven inlet temperature ranges from 180-200oC and oven outlet temperature ranges from 175-195oC;
e) cooling said heated compressed web at ambient temperature to obtain a densified thermal bonded polyester block.
6. The process for preparing densified thermal bonded polyester block as claimed in claim 6, wherein the amount of said conventional staple fiber ranges from 60-70%. ,TagSPECI:Field
The present disclosure relates to a densified thermal bonded polyester block and a method for its preparation.

Definitions
As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used to indicate otherwise.

Low melt fiber (LMF): A low melt fiber is produced by bi-component spinning of polyester and modified polyester. It can be melted at lower temperature (110~200oC) than normal fiber and can be bonded with other fibers.

Staple fiber: A mass of fibres having certain homogeneity of properties, usually length.

Bale opener: Bale opener is a machine and is used for opening bales of various types of materials such as fibers.

Carded web: A carded web is obtained by a process called carding, wherein the fibers are disentangled, cleaned and intermixed to produce a continuous web or sliver, suitable for subsequent processing. This is achieved by passing the fibres between relatively moving surfaces (moving pins, wires or teeth) covered with card clothing.

Web: Single or multiple sheets of fibre used in the production of nonwoven fabric.

Cross lapper: The basic function of a cross lapper is to accept a lightweight fiber web and produce a heavier web by laying the lightweight web in layers. In the process of doing this, the direction of the material flow is altered 90 degrees. In other words, the fabric turns a corner.

Background
Polyurethane is a polymer composed of a chain of organic units joined by carbamate (urethane) links. Polyurethane blocks are generally used in the manufacture of flexible, high –resilience block seating, rigid block insulation panels and microcellular block seals and gaskets. However, polyurethane blocks are not safe for use as it is carcinogenic in nature.

Hence, there is felt a need for a simple and cost effective process for the preparation polyester blocks that are safe for use. There is also a need for polyester blocks with improved tensile strength, tear strength and break elongation properties.

Objects
Some of the objects of the present disclosure which at least one embodiment is adapted to provide, are described herein below:
It is an object of the present disclosure to provide densified thermal bonded polyester blocks.

It is another object of the present disclosure to provide a process for preparing densified thermal bonded polyester blocks.

It is yet another object of the present disclosure to provide a process for preparing densified thermal bonded polyester blocks by utilizing hot flue gas from industrial processes.

It is still another object of the present disclosure to provide densified thermal bonded polyester blocks which have better durability.

It is another object of the present disclosure to provide an environment friendly, simple, safe and cost effective process for preparing densified thermal bonded polyester blocks.

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.

Summary
The present disclosure provides a densified thermal bonded polyester block having tensile strength ranging from 5-8 kg/cm2; tear strength ranging from 4-7 kg/cm, break elongation ranging from 115-130% and a density ranging from 58-63kg/m3 and a process for preparing the densified thermal bonded polyester block.
In the process of the present disclosure, 30-40% by weight of low melt fibers and conventional staple fibers are well mixed, carded and cross-lapped to build a web. The so obtained web is then compressed and a stream of hot flue gas is circulated through multiple channels into the compressed web so that the low melt fibers softens and forms a physical bond with the conventional staple fibers. The heated compressed web is then cooled to form a densified thermal bonded polyester block.

Detailed Description
The conventionally compressed synthetic web has limited thickness and is not thermo-bonded. It was assumed that difficulties would be encountered in making thick, thermo-bonded densified web due to localized heating at the surface of the web. Further, the previously known thermally bonded polyester fibers have limited strength and involve a number of process steps, making it labor intensive.

The inventors of the present disclosure envisaged a process for preparing a densified thermal bonded polyester block from low melt fibers and conventional staple fibers by passing hot flue gas through multiple channels to obtain a densified thermal bonded polyester block that has high tensile strength; high tear strength and low break elongation properties.
Furthermore, the inventors have optimized the temperature conditions and residence time of densified thermal bonded polyester blocks so as to soften the low melt fibers and form a physical bond with the conventional staple fibers.

In accordance with one aspect, the present disclosure provides a densified thermal bonded polyester block comprising
a. 30 to 40 % by weight of low melt fibers; and
b. Conventional staple fibers.

The densified thermal bonded polyester block is characterized by tear strength ranging from 4-7 kg/cm, tensile strength ranging from 5-8 kg/cm2, break elongation properties ranging from 115-130% and density ranges from 58- 63Kg/m3.
The low melt fibers used in the present disclosure are selected from the group consisting of polyester low melt fibers, nylon low melt fibers, and viscose rayon low melt fibers.
In one embodiment of the present disclosure, the low melt fibers are polyester low melt fibers.
The amount of low melt fibers used in the present disclosure ranges from 30-40% by weight of the polyester block.

The conventional staple fibers used in the present disclosure are selected from the group consisting of polyester staple fibers, viscose staple fibers and nylon staple fibers.
The amount of conventional staple fibers used in the present disclosure ranges from 60-70% by weight of the polyester block.
In one embodiment of the present disclosure, the conventional staple fibers are polyester staple fibers.

In accordance with another aspect, the present disclosure provides a process for preparing densified thermal bonded polyester block comprising the following steps:
In the first step, 30-40% by weight of low melt fibers and conventional staple fibers are mixed to obtain a fiber blends.
In the second step, so obtained fiber blends are fed into the conveyor line of a bale opener to obtain a carded web. The bale opener is a simple lattice with spikes and has a roller on top of the open fibers. At one end of the bale opener, there is provided a pre-opener from where the fibers are transferred to the auto leveler by air suction. Below the auto leveler there is a fine opener and fibers are transferred to the vibrating feed hopper by air suction. Dual cylinders and dual doffers positioned on the bale opener feed two separate carded web to the cross lapper.
In the third step, the cross lapper compresses the carded web and puts them in the lattice for entering in the oven area.
In the fourth step, said compressed web obtained from the cross lapper (third step) is fed in an oven through a conveyer line and a stream of hot flue gas is passed into said compressed web through the multiple channels to obtain heated compressed web. The inlet temperature of the oven ranges from 180-200oC and the outlet temperature of oven ranges from 175-195oC. The residence time of the compressed web in the oven area is 10-20 minutes. Hot flue gases are cross circulated in the oven after passing through multiple channels. Due to cross circulation of hot flue gases, the densified thermal bonded polyester block so produced has improved properties such as high strength and low break elongation property.
In the fifth step of the present disclosure, the so obtained heated compressed web is taken out from the oven and cooled at an ambient temperature to obtain a densified thermal bonded polyester block.
The densified thermal bonded polyester block is characterized by tear strength ranging from 4-7 kg/cm, tensile strength ranging from 5-8 kg/cm2, break elongation properties ranging from 115-130% and density ranging from 58- 63Kg/m3.

The process of the present disclosure can be used for preparing densified thermal bonded polyester block having density ranging from 40-80kg/m3 by varying the oven temperature and residence time.

The present disclosure is further illustrated herein below with the help of the following examples. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of embodiments herein.

Experimental details:
Example 1: preparation of a densified thermal bonded polyester block:
The densified thermal bonded polyester block was prepared by mixing 35kg of polyester low melt fibers, 65kg of conventional polyester staple fibers to obtain a fiber blends. The obtained fiber blend was fed into the conveyor line of a bale opener followed by feeding into the carding machine to obtain a web. The obtained web was directed into the ‘cross lapper’ which in turn folds the webs and puts them in the lattice entering the oven area. The compressed web was then fed into an oven through a conveyer line and a stream of hot flue gas was passed into the compressed web through multiple channels to obtain heated compressed web. The oven inlet zone temperature was kept at 190oC. The so obtained heated compressed web was kept in oven at a temperature 185oC for 18 minutes. The heated compressed web was then taken out from oven and cooled to an ambient temperature to obtain densified thermal bonded polyester block. The obtained densified thermal bonded polyester block has a density 60kg/m3, as characterized by a mechanical testing machine.

The preparation parameters are given in the Table 1 below.

Table 1:
Production & Quality Report for 60kg/m³ density blocks
Fiber used: Preblended
Oven Inlet zone temperature°C 190°C
Residence Time (min.) 18 Minutes
Oven outlet zone temperature°C 185°C

Example 2: Characterization of densified thermal bonded polyester block for various properties:
The densified thermal bonded polyester block obtained from example 1 was characterized by IS: 7888 method for density, tensile strength, break elongation, load quotient, indentation hardness and compression set.
The test was carried out for average, minimum and maximum reading for the above said parameters. The details of test results are given in Table 2.

Table 2:
Sr.no. Properties Test Method Specs. C-K607 (Rev.-1) Results
1 Density(kg/m³) IS: 7888 Cl.4 60±3
Avg 60.35
Min 58.23
Max 62.51
2 Tensile Strength(kg/cm²) IS: 7888 Cl.5 Min 4.0
Avg 6.5
Min 5.12
Max 7.36
3 Elongation at break (%) IS: 7888 Cl.5 Min 110
Avg 121.33
Min 118
Max 126
4 Load quotient IS: 7888 Cl.6 Min. 4:1
Avg 9.49
Min 8.68
Max 10.14
5 Indentation hardness at 25% (kgf) IS: 7888 Cl.6.3.3 21-30
Avg 24.46
Min 23.22
Max 25.67
Indentation hardness at 40% (kgf) 46-56
Avg 52.3
Min 49.53
Max 55.95
6 Compression Set- 50% at room temperature. (27+2⁰C) for 70 hrs. (%) IS: 7888 Cl.8 Max 10
Avg 9.24
Min 9.05
Max 9.54

Example 3: Characterization of densified thermal bonded polyester block for tear strength, delamination test, humidity ageing and resilience: The densified thermal bonded polyester block obtained from example 1 was characterized by ISO: 8067 method for tear strength and delamination test. Humidity ageing test for hardness loss was characterized by ISO: 2440 and resilience (%) was characterized by ISO: 8307 method.
The test was carried out for average, minimum and maximum reading for the above said parameters. The details of test results are given in Table 3.

Table 3:
Sr.no. Properties Test Method Specs. C-K607 (Rev.-1) Results
1 Tear Strength (kg/cm) ISO:8067 Min 1.5
Avg 5.15
Min 4.31
Max 6.12
2 Delamination test (Parallel) ISO:8067 Min 2.5N/2.5cm
Avg 5.37
Min 4.57
Max 6.22
3 Humidity ageing test Hardness loss (%) ISO :2440 Max 13
Avg 12.02
Min 11.47
Max 12.36
4 Resilience (%) ISO:8307 Min 45
Avg 52
Min 50
Max 53

Example 4: Characterization of densified thermal bonded polyester block for resistance to spread of flame and deterioration of visibility due to smoke:
The densified thermal bonded polyester block obtained from example 1 was characterized by Appendix-8 of UIC 564-2 OR method for resistance to spread of flame and deterioration of visibility due to smoke
The test was carried out for average, minimum and maximum reading for the above said parameters. The details of test results are given in Table 4.

Table 4
Sr.no. Properties Test Method Specs. C-K607 (Rev.-1) Results
1 Resistance to spread of flame Appendix-8 of UIC 564-2 OR Class-B (min)
Avg A
Min A
Max A
2 Deterioration of visibility due to smoke Appendix-15 of UIC 564-2 OR Class-A
Avg A
Min A
Max A

Example 5: Characterization of densified thermal bonded polyester block for limiting oxygen index and toxicity:
The densified thermal bonded polyester block obtained from example 1 was characterized by IS: 13501 method for limiting oxygen index; and NCD: 1409 for toxicity index. The test was carried out for average, minimum and maximum reading for the above said parameters. The details of test results are given in Table 5.

Table 5
Sr.no. Properties Test Method Specs. C-K607 (Rev.-1) Results
1 Limiting Oxygen Index IS:13501 28 (min)
Avg 30.33
Min 30
Max 32
2 Toxicity Index NCD:1409 Less than 1.0
Avg 0.458
Min 0.458
Max 0.458

Technical advantages:

 The densified thermal bonded polyester blocks are non-toxic.
 The densified thermal bonded polyester blocks have comparatively high tear strength; high tensile strength and low break elongation properties.
 The process for the preparing highly densified thermal bonded polyester block is simple and cost effective.

The exemplary embodiments herein quantify the benefits arising out of this disclosure and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments 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.