Composition and method for making reinforcement for footwear

Abstract

The microporous shoe reinforcement has at least one adhesive layer coextruded with and supported on a reinforcement core. A liquid, such as liquid nitrogen, is introduced into the extruder for the reinforcement core to produce a closed-cell foam with a gaseous component. The gas reduces the weight and cost of the reinforcement without significantly reducing hardness and elasticity.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 928,858, filed on October 31, 2019, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to reinforcements, such as those used in the manufacture of shoes to maintain the shape of the heel and toe portions of the shoe. Background Art

[0004] Box toes and heels are used on the front and back of a shoe to provide shape and stiffness. There are many different types of stiffeners used in the shoe industry for box toes and heels. U.S. Patent Nos. 3,523,103, 3,590,411, 3,647,616, 3,891,785, 3,973,285, 4,814,037, 6,391,380, 6,475,619, and 7,976,404 disclose methods and materials for increasing the stiffness and bonding qualities of materials used in the shoe industry (all of which are incorporated herein by reference). The hardened plastic resin is selected from styrene butadiene, polystyrene, polyvinyl acetate, acrylic, and other polymer lattices that can be impregnated into the needle-punched nonwoven fabric. Some of these types of reinforcements are coated with a hot melt adhesive on their surface and are heat activated to bond to the upper and lining. Some are solvent activated and do not contain heat activated hot melt adhesive. The second group of reinforcements are preformed materials made of polyvinyl chloride, ionomers, or thermoplastic rubber (TPR). These preformed reinforcements require an adhesive to be coated on the surface to bond to the components of the shoe. Some reinforcements are made by extruding a resin (such as an ionomer or other thermoplastic polymer), which then requires an adhesive to be extruded onto a polymer sheet. The last category includes reinforcements made from powders, which are a mixture of fillers or hard materials with an adhesive or softer material. These polymer powder mixtures are then heat sintered to produce reinforcements.

[0005] The ideal properties of a reinforcement are high elasticity and good hardness for a given weight of material. Saturated reinforcements can be made hard, but generally the harder grades are not highly elastic. Saturated reinforcements, preformed reinforcements, and extruded reinforcements all require an additional processing step to apply the adhesive to the surface. Powder-coated reinforcements generally require cryogenic grinding to produce a fine powder from a low melting point adhesive, which results in increased cost and the need for a critical particle size distribution. Powder-coated materials, because they are sintered, also have lower toughness or strength and require additional weight to obtain a given hardness because the sintering action does not form a true melt of the material to maximize physical properties. These materials also require a high level of adhesive content to bond well to the various substrates to which they will be attached. This adds additional cost and additional weight. When hot-melt saturated materials or extruded materials, they require a large amount of hot-melt adhesive to be applied to their surface in a separate step.

[0006] In some processes and products used in the packaging industry, a tie layer of adhesive is added to another resin to create a very thin layer to bond these different layers together. Typically this is done with an adhesive tie layer where the melt viscosity and melting point of the adhesive component is similar to the other layers. The method of producing these materials is an extrusion process using multiple extruders and multi-component modules or manifold dies.

[0007] An object of the present invention is to provide a material for box toe caps and heels which has maximum stiffness and minimum material weight. Summary of the invention

[0008] The first embodiment relates to a hard but lightweight box toe material or back material for shoes. High hardness and low weight are achieved by using a foam core material to manufacture a reinforcement member, which is made by introducing a gaseous material into the core of the reinforcement member to reduce weight without reducing the hardness of the material. DETAILED DESCRIPTION

[0009] One embodiment of the present invention is a sheet that can be three layers thick, where the two outer layers are adhesive and the core layer provides most of the stiffening effect. This can be called an A / B / A type sheet, where the B layer or core is the hardest.

[0010] In one embodiment, the sheet is made using two extruders, one extruder producing the outer two layers (i.e., the A layer of the A / B / A sheet) and the second extruder producing the core layer (i.e., the B layer of the A / B / A sheet), and this embodiment uses a three-layer manifold die. The outer layers of one embodiment are thermoplastic polyurethanes, such as BASFAH 652, which has a melting point of 70-80°C and a melt flow index of 10+ / -3. The core layer contains 86% Eastman GN071 PETG copolyester (specific gravity of 1.27, deformation temperature of 70°C) and 14% Exxon Exact 9071 thermoplastic polyolefin elastomer (density of 0.870, melt flow rate of 0.5g / 10min and glass transition temperature (Tg) of 54F).

[0011] The extruded material from the die can be calendered into sheets. Sheets can have various thicknesses and weights depending on the specific end use. Sheets are typically sampled and hardness tested using the Satra™ 83 test procedure.

[0012] An alternative embodiment of the above formulation for the core material could be a core formulation that utilizes harder materials that are recycled and ground and then put back into the core. The core could also be recycled PETG. This sheet of this alternative embodiment could have the same outer layers as the first embodiment, but the core would be 51% GN071, 35% recycled material, 14% Exact.

[0013] For any of these embodiments, a novel and surprisingly beneficial aspect of the invention involves introducing liquid nitrogen into the last section of the extruder barrel. The liquid nitrogen mixes with the molten plastic resin, and when the molten material leaves the extruder / die, it forms a gaseous material and a closed-cell foam in the core. This aspect of the disclosure provides a lower density product that is lighter in weight but still similar in hardness, as will be illustrated in the examples below. Teachings related to the introduction and control of nitrogen in extruded polymer materials are disclosed in U.S. Patent No. 6,616,434, the disclosure of which is incorporated herein by reference.

[0014] Example 1

[0015] This example compares the operation of the above formulation with and without gas without circulation in the core. The core extruder contained 86% PETG and 14% TPE and the outer layer extruder contained TPU. The core was run at 185 lbs / hr and the outer layer at 85 lbs / hr. The samples were extruded into a die into a calender roll to cool and set the thickness. One set of samples was run without any gas and the second set of samples had 0.028% nitrogen added to the core. The results of the Satra test method are shown below for the no gas control sample and the sample containing nitrogen added to the melt of the extruder.

[0016] Sample type No gas There is gas No gas There is gas Thickness, mm 0.89 0.90 1.29 1.33 <![CDATA[Weight, g / m 2 > 947 758 1399 1038 The first collapse, KG 7.0 5.5 16.0 10.5 The 10th collapse, KG 6.8 4.1 15.6 7.1 Shape retention, % 98 98 98 97 Rebound rate, % 97 75 97 68

[0017] If 1038g / m 2 The gas sample and 947g / m 2 Compared with the gas-free sample, the hardness is 10.5 and 7.0 respectively, the hardness increases by 50%, but the weight increases by only 9.6%, or in order to achieve a hardness value of 7, the gas sample only needs to weigh 692g / m 2 or a 27% reduction in weight. As mentioned above, the gas is nitrogen, which is injected into the extrusion process of the core as liquid nitrogen.

[0018] Example 2

[0019] This example was run with PET from New Era, with an intrinsic viscosity of 0.825, instead of PETG. The extruder temperature profile for zones 1-5 was 350F, 510F, 520F, 500F, and 400F, with liquid nitrogen injected into zone 5. The formulation ratios were the same as above.

[0020] Sample type There is gas There is gas There is gas No gas Thickness, mm 1.06 1.06 1.16 0.91 <![CDATA[Weight, g / m 2 > 1040 899 917 1077 The first collapse, KG 14 12.1 14.0 14.5 The 10th collapse, Kg 12 9.1 11.4 10.4 Shape retention, % 97 92 99 99 Rebound rate, % 86 75 84 72

[0021] For this example, a gas sample weighing 899 would have to be 1045 g / m 2 To have the same 1st collapse, this represents a 3% reduction in weight and lower density. Weight is 917g / m 2 The above gas sample weighs 15% less than the non-gas sample and has essentially the same 1st collapse or hardness as the non-gas sample, and by comparing the gas sample weighing 917 to the non-gas sample weighing 1077, the gas sample weighs about 15% less. The gas sample weighing 1040 will also weigh about 3% less than the non-gas sample and have essentially the same 1st collapse. However, the gas sample weighing 917 has a higher 10th collapse, which provides better elasticity and final hardness.

[0022] Example 3

[0023] This example uses the above PETG formulation with recycled content included in the core material, as shown below, with a 14% weight reduction based on achieving the same 1st collapse hardness as the no gas sample.

[0024] Sample type No gas There is gas Thickness, mm 1.04 1.04 <![CDATA[Weight, g / m 2 > 1191 1026 The first collapse, KG 11.4 11.2 The 10th collapse, Kg 10.0 8.0 Shape retention, % 98 96 Rebound rate, % 82 71

[0025] Example 4

[0026] The core material in this example is 86% PETG and 14% TPE, and the outer 2 layers are PETG.

[0027] The extrusion rate for the core was 75 lbs / hr and the total extrusion rate for the outer layers was 30 lbs / hr.

[0028]

[0029]

[0030] This foam has a 5% reduction in weight at a higher 1st collapse. If the collapse is adjusted to the no foam value, the weight drops to 1145, a reduction of 8%.

[0031] Based on the above tests, a PETG / TPE core or PETG / TPE plus recycled core or PET / TPE core formulation can be used and the hardness of the material can be made similar to that of a heavier material by injecting 0.028% liquid nitrogen into the extruder to create a gas bubble in the product, which will reduce the weight and will not negatively affect the hardness.

[0032] Example 5

[0033] This example is an ABA material, wherein the A layer is 14% of the total weight and the core is 86%; a control sample made of a core (composed of 56% PETG, 30% recycled material, 9% elastomer and 5% polyurethane) is compared with a gas sample made of a core (70% PETG, 30% recycled material, 0.0217% gas and 0.014% MU Talc NB 27 (MuCell Company nucleating agent)), and the outer layer of the sample is the above-mentioned TPU material.

[0034]

[0035]

[0036] The weight was reduced by 17%, but the hardness determined by the 1st collapse was still similar to the control (i.e., the sample without gas), and the elasticity was good even after the elastomer and polyurethane were removed because the gas helped to improve the elasticity compared to a material made without elastomer and polyurethane and with a higher PETG content (which would be harder and have a lower rebound rate).

[0037] Example 6

[0038] This example represents the use of this foaming technology on a more flexible material where the material does not lose flexibility or hardness when comparing the control to the foamed sample. This is also an ABA material but with a more flexible core. The A layer is the same as above at 23% of the total weight and the control core is composed of 25% PETG, 23% recycled material, 26% AH-652TPU and 26% recycled polyurethane. The prepared gassed sample is composed of 40% PETG, 11% TPUAH-652, 23% recycled material and 26% recycled polyurethane with 0.02% nitrogen and 0.014% MuTalc NB27. The extra PETG is to increase the hardness as the weight is lighter by aeration but helps with flexibility to overcome the situation of having extra PETG and less TPU.

[0039] Sample type No gas There is gas Thickness, mm 0.54 0.53 <![CDATA[Weight, g / m 2 > 634 539 The first collapse, KG 1.29 1.22 The 10th collapse, Kg 1.11 1.03 Shape retention, % 98 98 Rebound rate, % 86 84

[0040] The weight is reduced by 15%, but the stiffness and rebound are very similar, there is no loss in taking out the TPU and adding extra PETG for stiffness, as the gas makes up for the disappearance of some of the TPU and still provides very good springiness / flexibility.

[0041] Example 7

[0042] This embodiment represents an A / B / A structure, wherein the A layer is 98% low-temperature TPU and 2% antiblock, and the B core layer is 45% recycled material (65.9% PETG, 14.9% TPE elastomer, 18.9% TPU, 0.4% antiblock), 30% TPE elastomer, and 25% recycled polyurethane.

[0043] A layer is 183g / m 2 , B layer is 629g / m 2 .

[0044] The foaming material is the same A layer, the foaming core layer is 55% recycled material (65.9% PETG, 14.9% TPE elastomer, 18.9% TPU, 0.4% anti-adhesion material), 30% TPE elastomer, 15% recycled polyurethane, 0.015%-0.025% nitrogen and 0.15%-0.25% nucleating agent. The weight of the A layer is 187g / m 2 , the weight of layer B is 505g / m 2 .

[0045] Here are the test results:

[0046] Sample type No gas There is gas Thickness, mm 0.75 0.76 <![CDATA[Weight, g / m 2 > 812 693 The first collapse, KG 1.20 1.35 The 10th collapse, KG 0.95 1.20 Rebound rate, % 79.5 88.9

[0047] These data show that the gas samples weighed 15% less but still had the same or greater first collapse.

[0048] Example 8

[0049] This example is an A / B / A structure, but with a 50 g / m2 laminate on one side. 2 Polyester spunlace fabric.

[0050] Layer A is 98% low melting point TPU and 2% anti-adhesive material

[0051] The B layer is 45% recycled material (65.9% PETG, 14.9% TPE elastomer, 18.9% polyurethane, 0.4% anti-adhesion material), 30% TPE, and 25% recycled polyurethane.

[0052] A layer is 187g / m 2 , B layer is 643g / m 2 .

[0053] The foam material also has an A / B / A structure, wherein the composition of the A layer is as described above. The B layer is 55% recycled material (65.9% PETG, 14.9% TPE elastomer, 18.9% TPU, 0.4% anti-blocking material), 30% TPE elastomer, 15% recycled polyurethane, 0.015%-0.025% nitrogen and 0.15-0.25% nucleating agent.

[0054] A layer is 187g / m 2 , B layer is 506g / m 2 .

[0055] Here are the test results:

[0056] Sample type No gas There is gas Thickness, mm 0.92 0.92 <![CDATA[Weight, g / m 2 > 880 743 The first collapse, KG 1.80 1.64 The 10th collapse 1.42 1.34 Rebound rate, % 79 82

[0057] The total weight was reduced by 16.5%, the core weight was reduced by 21.3%, and the dome values ​​were similar.

[0058] For Examples 7 and 8, the TPU used in the A layer had a melting point of 50-60°C, a Shore A hardness of 97, and a melt flow of 10 + / - 5 g / 10 min at 150°C.

[0059] The melting point of polyurethane is between 65-90°C, with the same hardness and melt flow index.

[0060] Example 9

[0061] This example is based on the use of polyethylene vinyl acetate, EVA polymer.

[0062] The VA content of EVA#1 is 17.8%, the melt index is 0.34 g / 10 min, and the peak melting point is 88°C.

[0063] The VA content of EVA#2 is 27.5%, the melt index is 25 g / 10 min, and the peak melting point is 71°C.

[0064] The control product without foam and the foamed product both have an A / B / A structure, and the same A structure contains 34% EVA#1 and 64% EVA#2 and 2% anti-blocking material.

[0065] The core of the unfoamed control product contained 34% EVA #1 and 66% EVA #2.

[0066] The core of the foamed product contains 34% EVA#1, 66% EVA#2, 0.015-0.025% nitrogen and 0.15-0.25 nucleating agent.

[0067] Here are the test data:

[0068]

Claims

1. A microcellular foam toe reinforcement material or a back reinforcement material, comprising a reinforcement core having a first surface and a second surface relative to each other, and a first adhesive layer co-extruded with the reinforcement core and loaded on the first surface of the reinforcement core; the reinforcement core is made of a polymer material and nitrogen; wherein the polymer material is 86 weight % of polyethylene terephthalate and 14 weight % of a thermoplastic polyolefin elastomer, or the polymer material is 86 weight % of polyethylene terephthalate and 14 weight % of a thermoplastic polyolefin elastomer; the nitrogen is 0.028 weight % of the reinforcement core. 2 . The microcellular foam toe reinforcement material or the back reinforcement material according to claim 1 , further comprising a second adhesive layer co-extruded with the reinforcement core and loaded on the second surface of the reinforcement core. 3 . The microcellular foam toe reinforcement material or the back reinforcement material according to claim 2 , wherein the first adhesive layer and the second adhesive layer are low melting point polyurethane.

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