A method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric

Abstract

This invention discloses a method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric, comprising the following steps: S1, configuring raw material fibers, polyester staple fibers and water-soluble staple fibers in a certain proportion; S2, mixing the raw material fibers with an oiling agent, opening, blending, carding, and laying to obtain a fiber web; S3: pre-punching the fiber web, and then reinforcing the fiber web by alternating main punching on both sides to obtain a nonwoven fabric blank; S4: introducing the nonwoven fabric blank into hot water to dissolve and remove water-soluble fibers, and then squeezing to remove water and drying to obtain a liquid-containing nonwoven fabric with a predetermined liquid content; S5, introducing the liquid-containing nonwoven fabric into a hot rolling device, and then heat-setting to obtain the finished nonwoven fabric. This method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric incorporates vinylon into the raw material fibers; hot water treatment causes the vinylon to dissolve, leaving gaps in the entangled fiber web; after high-temperature heat setting, the cohesion between polyester fibers is moderate, resulting in a dimensionally stable, high-temperature resistant, high-elongation, and soft, fluffy polyester needle-punched nonwoven fabric.

Description

Technical Field

[0001] This invention relates to the field of nonwoven fabric production technology, specifically to a method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric. Background Technology

[0002] Nonwoven fabrics used as the base material for automotive seat leather need to possess excellent high-temperature resistance, longitudinal / transverse elongation, low heat shrinkage, and suitable softness and hardness. In needle-punched nonwoven products, fibers are inserted into the fiber web through needles with side teeth, hooked onto the side teeth, and penetrate the fiber web with the needles. The needles penetrate from different surfaces of the fiber web, causing the fibers to entangle with each other, and the fiber web is reinforced to form a nonwoven fabric as a whole.

[0003] The type of fiber in nonwoven fabric determines the cohesion and shrinkage force between the fibers. When elastic fibers such as spandex are stretched, the helical structure of the fibers changes, and the fibers can return to their original length after the tension is removed; while the elasticity of polyester fibers mainly comes from the deformation capacity of the fibers, and when polyester undergoes stretching deformation, its recovery speed is slower.

[0004] To achieve the desired dimensional stability, the polyester nonwoven fabric needs to undergo a heat-setting process. During this process, the shrinkage of entangled fibers increases the cohesion between fibers at the entanglement points, negatively impacting the fabric's elongation and bulk. Furthermore, the bulk of the nonwoven fibers determines its stiffness and the adhesion area to leather foaming materials, the latter further affecting the strength of automotive seat leather. An improved method involves reducing the degree of fiber entanglement in the polyester nonwoven fabric before heat setting, but this results in lint shedding from the fabric surface. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in the existing technology and provide a method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric. Vinylon participates in the entanglement of nonwoven fabric fibers, and the voids generated by its dissolution work together with the shrinkage of polyester fibers during heat setting to produce a needle-punched nonwoven fabric with moderate fiber cohesion, high elongation, and soft hand feel.

[0006] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: a method for producing high-elongation, high-temperature resistant needle-punched nonwoven fabric, comprising the following steps:

[0007] S1. Prepare raw material fibers, including polyester staple fiber and water-soluble staple fiber, in proportion.

[0008] S2. Raw fiber is mixed with oil agent, opened, blended, combed, and laid to obtain fiber web;

[0009] S3: Pre-punched fiber web, then the fiber web is reinforced by alternating main punching on the front and back sides to obtain nonwoven fabric blank;

[0010] S4: The nonwoven fabric blank is introduced into hot water to dissolve and remove water-soluble fibers, and then squeezed to remove water and dried to obtain a liquid-containing nonwoven fabric with a predetermined liquid content.

[0011] S5: The liquid-laden nonwoven fabric is fed into the hot rolling equipment and heat-set to obtain the finished nonwoven fabric.

[0012] A preferred technical solution is that the water-soluble fiber is vinylon, and the mass percentage of vinylon in the raw material fiber is 0.5% to 4%.

[0013] A preferred technical solution is that the fiber web has a layered structure of at least three layers, the fiber web includes a polyester fiber web layer and a mixed fiber web layer, the water-soluble fiber is disposed in the mixed fiber web layer, and the surface layer of the fiber web is all polyester fiber web layer; the mass percentage of vinylon in the mixed fiber web layer is not higher than 20%.

[0014] The preferred technical solution is that the polyester fineness is 2.7 to 3.1 dtex, the average elongation of the polyester fiber is 140% to 175%, and the vinylon fineness is 1.4 to 1.7 dtex.

[0015] The preferred technical solution is that the length of the polyester staple fiber is 55-70mm and the length of the vinylon staple fiber is 30-45mm.

[0016] The preferred technical solution is that both the pre-needling and main needling use Y-shaped needles, the pre-needling depth of the fiber mesh is 8-10 mm, and the needle density is 1200-1500 needles / cm². 2 The needling frequency is 400–500 times / min; the main needle insertion depth is 7–9 mm; and the needling density is 2500–3200 needles / cm². 2 The needle punching frequency is 700-850 times / min; the feeding speed of S3 fiber web is 3-5m / min.

[0017] The preferred technical solution is that the amount of the polyester web layer oiling agent added is 0.7% to 1.1% of the fabric mass, and the amount of the mixed web layer oiling agent added is 1.3% to 1.6% of the fabric mass.

[0018] The preferred technical solution is that the hot water temperature of S4 is 65-80℃.

[0019] The preferred technical solution is that the liquid content of the liquid-containing nonwoven fabric is 1.5% to 6.5%, and the heat setting temperature of the hot rolling equipment is 195 to 205°C.

[0020] The preferred technical solution is that the basis weight of the finished nonwoven fabric is 310-330 g / m². 2 The thickness is 0.9 to 1.05 mm.

[0021] The advantages and beneficial effects of this invention are as follows:

[0022] The production method of this high-elongation, high-temperature resistant needle-punched nonwoven fabric involves adding vinylon to the raw fiber and laying it into a web, pre-punching, and needle-punching to obtain a nonwoven fabric blank. Vinylon has lower elasticity and resilience than polyester. When vinylon and polyester are hooked by needles and pierced into the fiber web at the same time, it helps to reduce the tensile force of the needles on the polyester. Vinylon and polyester are simultaneously entangled in the reinforcing fiber web.

[0023] Hot water treatment causes the vinylon to dissolve, leaving gaps in the entangled fiber web and reducing the web density; high-temperature heat setting treatment causes the polyester fibers to shrink, reducing the gaps and making the cohesion between polyester fibers moderate, resulting in a polyester needle-punched nonwoven fabric that is dimensionally stable, heat-resistant, has high elongation, and is soft and fluffy to the touch. Detailed Implementation

[0024] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0025] Example 1

[0026] Example 1: The production method of high-elongation, high-temperature resistant needle-punched nonwoven fabric includes the following steps:

[0027] S1. Polyester staple fiber and vinylon staple fiber are configured at a fiber weight ratio of 97:3. According to the raw material quality test, the polyester fineness is 3.01 dtex, the average elongation is 164%, and the length of the polyester staple fiber is 66 mm; the vinylon fineness is 1.53 dtex, and the length of the vinylon staple fiber is 42 mm.

[0028] S2. The raw material fibers are configured into two parts: one is 100% polyester staple fiber, and the other is 92% polyester staple fiber and 8% vinylon staple fiber (mixed fiber).

[0029] Takemoto FDY oil was prepared into a 10% aqueous solution and applied to 100% polyester staple fiber at an oiling rate of 0.8% and to mixed fibers at a rate of 1.45%. The fibers were pre-opened, mixed, opened, and carded with double cylinders and double doffers to form a thin fiber web. The web was laid with 100% polyester staple fiber on the surface and mixed fibers in the middle layer, with a total of 11 layers. Among them, the mixed fiber web layer formed by the mixed fibers consisted of 4 layers, which were alternately layered with the polyester fiber web.

[0030] S3: The clamping feeder clamps the fiber web and feeds it into the needle area at a feeding speed of 4m / min;

[0031] The pre-punched fiber mesh uses Y-shaped needles, with a punching depth of 9.5 mm and a punching density of 1400 needles / cm². 2 The acupuncture frequency was 450 times / min;

[0032] The main barbed wire mesh has Y-shaped barbs with a penetration depth of 8 mm and a barb density of 2600 barbs / cm². 2 The needle punching frequency is 780 times / min, and the front and back sides of the fiber web are alternated three times: front punch, back punch, front punch, back punch, front punch, back punch, then the edges are cut to obtain the nonwoven fabric blank;

[0033] S4: The nonwoven fabric blank is introduced into hot water at 75°C to dissolve and remove the vinylon, then squeezed out of water by extrusion rollers and dried to obtain liquid-containing nonwoven fabric. The liquid-containing nonwoven fabric has a liquid content of 3.2%.

[0034] S5: The liquid-laden nonwoven fabric is fed into the hot rolling equipment at a feed rate of 17 m / min. The heat setting temperature of the hot rolling equipment is 200℃. After heat setting, the average basis weight is 311 g / m². 2 The finished nonwoven fabric has an average thickness of 0.98mm and a width of 1500mm.

[0035] Testing revealed that the tear strength of the nonwoven fabric in Example 1 was 10 kg (T) and 9.2 kg (Y); the breaking strength was 33.2 kg / 2.54 cm (T) and 35.9 kg / 2.54 cm (Y); the elongation at break was 96% (T) and 131% (Y); and the burst strength was 17.7 kgf / cm². 2 The softness / hardness is 3.8 (the higher the value, the softer the non-woven fabric feels).

[0036] Example 2

[0037] Example 2: The production method of high-elongation, high-temperature resistant needle-punched nonwoven fabric includes the following steps:

[0038] S1. Polyester staple fiber and vinylon staple fiber are configured according to a fiber mass ratio of 97:3, with the polyester staple fiber having a length of 66mm and the vinylon staple fiber having a length of 42mm.

[0039] S2. The raw material fibers are configured into two parts: one is 100% polyester staple fiber, and the other is 92% polyester staple fiber and 8% vinylon staple fiber (mixed fiber).

[0040] Takemoto FDY oil was prepared into a 10% aqueous solution and applied to 100% polyester staple fiber and mixed fiber at an oiling rate of 0.8%. The fiber was pre-opened, mixed with cotton, opened, and carded with double cylinders and double doffers to form a thin fiber web. The web was laid with 100% polyester staple fiber on the surface and mixed fiber in the middle layer, with a total of 11 layers. Among them, the mixed fiber web layer formed by the mixed fiber was 4 layers, which were alternately layered with the polyester fiber web.

[0041] S3: The clamping feeder clamps the fiber web and feeds it into the needle area at a feeding speed of 4m / min;

[0042] The pre-punched fiber mesh uses Y-shaped needles, with a punching depth of 9.5 mm and a punching density of 1400 needles / cm². 2 The acupuncture frequency was 450 times / min;

[0043] The main barbed wire mesh has Y-shaped barbs with a penetration depth of 8 mm and a barb density of 2600 barbs / cm². 2 The needle punching frequency is 780 times / min, and the front and back sides of the fiber web are alternated three times: front punch, back punch, front punch, back punch, front punch, back punch, then the edges are cut to obtain the nonwoven fabric blank;

[0044] S4: The nonwoven fabric blank is introduced into hot water at 75°C to dissolve and remove the vinylon, then squeezed out of water by extrusion rollers and dried to obtain liquid-containing nonwoven fabric. The liquid-containing nonwoven fabric has a liquid content of 3.2%.

[0045] S5: Feed the liquid-laden nonwoven fabric into the hot rolling equipment at a feed rate of 17 m / min. The heat setting temperature of the hot rolling equipment is 200℃. After heat setting, the average basis weight is 318 g / m². 2 The finished nonwoven fabric has an average thickness of 0.98mm and a width of 1500mm.

[0046] Testing revealed that the tear strength of the nonwoven fabric in Example 2 was 10.3 kg (T) and 9.4 kg (Y); the breaking strength was 33.7 kg / 2.54 cm (T) and 36.6 kg / 2.54 cm (Y); the elongation at break was 94.2% (T) and 128.6% (Y); and the burst strength was 18.0 kgf / cm². 2 Hardness 3.6.

[0047] The oiling rate of the mixed polyester and vinylon fibers is the same as that of 100% polyester fibers, which is not conducive to the adhesion between vinylon and polyester. The probability of the needle hooking both vinylon and polyester at the same time to puncture the fibers is reduced. The stretching of the punctured polyester is increased, and the shrinkage rate of the heat-set polyester fibers is greater. The degree of entanglement and cohesion between fibers in the nonwoven fabric is greater than that in Example 1. Compared with the change in strength, the breaking elongation is significantly reduced. Compared with Example 1, the fabric surface is slightly harder.

[0048] Example 3

[0049] Example 3: The production method of high-elongation, high-temperature resistant needle-punched nonwoven fabric includes the following steps:

[0050] S1. Polyester staple fiber and vinylon staple fiber are configured according to a fiber mass ratio of 97:3, with the polyester staple fiber having a length of 66mm and the vinylon staple fiber having a length of 42mm.

[0051] S2. The raw material fibers are configured into two parts: one is 100% polyester staple fiber, and the other is 92% polyester staple fiber and 8% vinylon staple fiber (mixed fiber).

[0052] Takemoto FDY oil was prepared into a 10% aqueous solution and applied to 100% polyester staple fiber at an oiling rate of 0.8% and to mixed fibers at a rate of 1.45%. The fibers were pre-opened, mixed, opened, and carded with double cylinders and double doffers to form a thin fiber web. The web was laid with 100% polyester staple fiber on the surface and mixed fibers in the middle layer, with a total of 11 layers. Among them, the mixed fiber web layer formed by the mixed fibers consisted of 4 layers, which were alternately layered with the polyester fiber web.

[0053] S3: The clamping feeder clamps the fiber web and feeds it into the needle area at a feeding speed of 4m / min;

[0054] The pre-punched fiber mesh uses Y-shaped needles, with a punching depth of 9.5 mm and a punching density of 1400 needles / cm². 2 The acupuncture frequency was 450 times / min;

[0055] The main barbed wire mesh has Y-shaped barbs with a penetration depth of 8 mm and a barb density of 2600 barbs / cm². 2 The needle punching frequency is 780 times / min, and the front and back sides of the fiber web are alternated three times: front punch, back punch, front punch, back punch, front punch, back punch, then the edges are cut to obtain the nonwoven fabric blank;

[0056] S4: The nonwoven fabric blank is introduced into hot water at 95°C to dissolve and remove the vinylon, then squeezed out of water by extrusion rollers and dried to obtain liquid-containing nonwoven fabric. The liquid-containing nonwoven fabric has a liquid content of 3.2%.

[0057] S5: The liquid-laden nonwoven fabric is fed into the hot rolling equipment at a feed rate of 17 m / min. The heat setting temperature of the hot rolling equipment is 200℃. After heat setting, the average basis weight is 313 g / m². 2 The finished nonwoven fabric has an average thickness of 0.98mm and a width of 1500mm.

[0058] Testing revealed that the tear strength of the nonwoven fabric in Example 3 was 10.6 kg (T) and 9.5 kg (Y); the breaking strength was 33.8 kg / 2.54 cm (T) and 36.3 kg / 2.54 cm (Y); the elongation at break was 92.7% (T) and 124.3% (Y); and the burst strength was 18.6 kgf / cm². 2 , hardness 3.3.

[0059] In Example 3, the nonwoven fabric preform was dissolved in hot water at a higher temperature to remove vinylon, while the polyester fibers were pre-shrinked freely in the hot water. The width of the nonwoven fabric before heat setting was smaller than that in Example 1. The strength of the nonwoven fabric was better than that in Example 1, the breaking elongation decreased, and the fabric surface became stiffer. Therefore, vinylon with a lower dissolution temperature is preferred as the water-soluble fiber to minimize the impact of the process on polyester shrinkage.

[0060] Example 4

[0061] Example 4: The production method of high-elongation, high-temperature resistant needle-punched nonwoven fabric includes the following steps:

[0062] S1. Polyester staple fiber and vinylon staple fiber are configured according to a fiber mass ratio of 97:3, with the polyester staple fiber having a length of 66mm and the vinylon staple fiber having a length of 42mm.

[0063] S2. The raw material fibers are configured into two parts: one is 100% polyester staple fiber, and the other is 92% polyester staple fiber and 8% vinylon staple fiber (mixed fiber).

[0064] Takemoto FDY oil was prepared into a 10% aqueous solution and applied to 100% polyester staple fiber at an oiling rate of 0.8% and to mixed fibers at a rate of 1.45%. The fibers were pre-opened, mixed, opened, and carded with double cylinders and double doffers to form a thin fiber web. The web was laid with 100% polyester staple fiber on the surface and mixed fibers in the middle layer, with a total of 11 layers. Among them, the mixed fiber web layer formed by the mixed fibers consisted of 4 layers, which were alternately layered with the polyester fiber web.

[0065] S3: The clamping feeder clamps the fiber web and feeds it into the needle area at a feeding speed of 4m / min;

[0066] The pre-punched fiber mesh uses Y-shaped needles, with a punching depth of 9.5 mm and a punching density of 1400 needles / cm². 2 The acupuncture frequency was 450 times / min;

[0067] The main barbed wire mesh has Y-shaped barbs with a penetration depth of 8 mm and a barb density of 2600 barbs / cm². 2 The needle punching frequency is 780 times / min, and the front and back sides of the fiber web are alternated three times: front punch, back punch, front punch, back punch, front punch, back punch, then the edges are cut to obtain the nonwoven fabric blank;

[0068] S4: The nonwoven fabric blank is immersed in hot water at 75℃ to dissolve and remove the vinylon, then squeezed by extrusion rollers to remove water and dry the nonwoven fabric.

[0069] S5: The dried nonwoven fabric is fed into the hot rolling equipment at a feed rate of 20 m / min and a heat setting temperature of 200℃; the average basis weight after heat setting is 318 g / m². 2 The finished nonwoven fabric has an average thickness of 0.98mm and a width of 1500mm.

[0070] Testing revealed that the tear strength of the nonwoven fabric in Example 4 was 10.1 kg (T) and 9.1 kg (Y); the breaking strength was 33.2 kg / 2.54 cm (T) and 35.8 kg / 2.54 cm (Y); the elongation at break was 95.4% (T) and 129.9% (Y); and the burst strength was 17.6 kgf / cm². 2 The hardness is 3.8; the liquid-containing nonwoven fabric has good dimensional stability before heat setting; compared with dry heat setting, the wet heat setting shrinkage rate of nonwoven fabric is larger, and the entangled part fills the gaps formed by the dissolution of vinylon.

[0071] Comparative Example

[0072] The production method of high-elongation, high-temperature resistant needle-punched nonwoven fabric includes the following steps:

[0073] S1. The polyester staple fiber is configured with a length of 66mm.

[0074] S2. Takemoto FDY oil agent is prepared into a 10% aqueous solution and applied to 100% polyester staple fiber at an oiling rate of 0.8%. The fiber is pre-opened, blended, main opened, and double cylinder double doffer carded into a thin layer web; the web is then laid in a cross-layered manner, with a total of 11 layers.

[0075] S3: The clamping feeder clamps the fiber web and feeds it into the needle area at a feeding speed of 4m / min;

[0076] The pre-punched fiber mesh uses Y-shaped needles, with a punching depth of 9.5 mm and a punching density of 1400 needles / cm². 2 The acupuncture frequency was 450 times / min;

[0077] The main barbed wire mesh has Y-shaped barbs with a penetration depth of 8 mm and a barb density of 2600 barbs / cm². 2 The needle punching frequency is 780 times / min, and the front and back sides of the fiber web are alternated three times: front punch, back punch, front punch, back punch, front punch, back punch, edge trimming, drying and humidification are applied to obtain a nonwoven fabric blank with a liquid content of 3.2%.

[0078] S5: Feed the liquid-laden nonwoven fabric into the hot rolling equipment at a feed rate of 17 m / min. The heat setting temperature of the hot rolling equipment is 200℃. After heat setting, the average basis weight is 320 g / m². 2 The finished nonwoven fabric has an average thickness of 0.99mm and a width of 1500mm.

[0079] Testing revealed that the comparative nonwoven fabric exhibited a tear strength of 11.5 kg (T) and 10.2 kg (Y); a breaking strength of 35.0 kg / 2.54 cm (T) and 37.5 kg / 2.54 cm (Y); a breaking elongation of 89.7% (T) and 121.8% (Y); and a burst strength of 19.4 kgf / cm². 2 The hardness is 3.5. The raw material fibers of the comparative nonwoven fabric do not contain vinylon. The fiber density and strength of the 100% polyester nonwoven fabric are higher than those of the example. However, when polyester is thermoformed and shrunken, there are no vinylon gaps to offset it, the fiber entanglement is tighter, and the elongation is smaller. It is not suitable as a base fabric for automotive seat leather with high elongation requirements.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a high-elongation, high-temperature resistant needle-punched nonwoven fabric, characterized in that, The method comprises the following steps: S1, proportionally configuring raw material fiber polyester fiber staple and water-soluble fiber staple; S2, opening, mixing, carding and laying the raw material fiber mixed with oil agent to obtain a fiber web; S3, pre-punching the fiber web, and then reinforcing the fiber web by alternately punching the front and back of the fiber web to obtain a non-woven fabric blank; S4, introducing the non-woven fabric blank into hot water to dissolve and remove the water-soluble fiber, and then extruding, drying to obtain a predetermined liquid-carrying non-woven fabric with liquid; S5, introducing the liquid-carrying non-woven fabric into a hot rolling device for hot setting treatment to obtain a non-woven fabric product; The fiber web is a laminated structure of at least three layers, which comprises a polyester fiber web layer and a mixed fiber web layer, the water-soluble fiber is arranged in the mixed fiber web layer, and the surface layer of the fiber web is the polyester fiber web layer; the mass percentage of the polyvinyl alcohol fiber in the mixed fiber web layer is not higher than 20%; the added amount of the oil agent in the polyester fiber web layer is 0.7% to 1.1% of the fabric mass, and the added amount of the oil agent in the mixed fiber web layer is 1.3% to 1.6% of the fabric mass.

2. The production method of high elongation high temperature resistant needle punched nonwoven fabric according to claim 1, characterized in that, The water-soluble fiber is polyvinyl alcohol fiber, and the mass percentage of the polyvinyl alcohol fiber in the raw material fiber is 0.5% to 4%.

3. The method of claim 1, wherein the high-elongation, high-temperature-resistant needle punch nonwoven fabric is produced by the steps of: The polyester fiber has a fineness of 2.7 to 3.1 dtex, and an average elongation of 140% to 175%; the polyvinyl alcohol fiber has a fineness of 1.4 to 1.7 dtex.

4. The production method of the high-elongation high-temperature-resistant needle punch nonwoven fabric according to claim 1 or 3, characterized by, The length of the polyester fiber staple is 55 to 70 mm, and the length of the polyvinyl alcohol fiber staple is 30 to 45 mm.

5. The method of producing a high-elongation high-temperature-resistant needle punch nonwoven fabric according to claim 1, characterized by, The preneedling and main needling use Y-shaped needles, the preneedling depth of the fiber web is 8-10 mm, the needling density is 1200-1500 needles / cm 2 , and the needling frequency is 400-500 times / min; the main needling depth is 7-9 mm, the needling density is 2500-3200 needles / cm 2 , and the needling frequency is 700-850 times / min; the feeding speed of the S3 fiber web is 3-5 m / min.

6. The method of producing a high-elongation, high-temperature-resistant needle punch nonwoven fabric according to claim 1, characterized by, The temperature of the hot water in S4 is 65 to 80℃.

7. The method of producing a high-elongation, high-temperature-resistant needle punch nonwoven fabric according to claim 1, characterized by, The liquid-carrying non-woven fabric has a liquid-carrying rate of 1.5% to 6.5%, and the hot setting temperature of the hot rolling device is 195 to 205℃.

8. The method of producing a high-elongation, high-temperature-resistant needle punch nonwoven fabric according to claim 1, characterized by, The nonwoven fabric product has a weight of 310 to 330 g / m 2 and a thickness of 0.9 to 1.05 mm.