TWI457084B - Polyolefin foamed composition and polyolefin foamed midsoles - Google Patents

Description

Polyolefin foam composition and shoe midsole made by the polyolefin foam

This invention relates to a polyolefin foam composition, and more particularly to a polyolefin foam composition for making a lightweight midsole.

The shoes have the function of protecting the feet. To make the user feel comfortable and reduce the burden, lightweight has become an important appeal for shoes. A foam composition having a polyolefin such as ethylene/vinyl acetate copolymer (EVA) as a plastic substrate has been widely used in the manufacture of shoe parts.

The foam used for the manufacture of the midsole of the shoe should have excellent properties such as elasticity, pressure resistance, appropriate softness and low density. The excellent elasticity can effectively absorb the vibration transmitted from the ground during walking and slow down the impact on the foot. The compression resistance can make the midsole of the shoe bear the weight of the user and is not easily deformed. The appropriate softness and hardness can be used on the one hand. The person feels comfortable when wearing shoes, on the other hand, it can effectively isolate sharp and hard objects on the ground, and the low density can reduce the weight of the shoes, thereby reducing the burden on the user.

It is known that the foam made of the polyolefin foam composition exhibits a density and mechanical properties in addition to the type of the plastic substrate, and is more uniform with the pore size, the number of pores, and the pore size of the foam. It is closely related. When the pores of the foam are large, a foam having a lower density can be obtained, but the mechanical properties of the foam are lowered, such as low hardness, easy collapse, elastic deterioration, tensile strength and tear resistance. The strength is low and so on. If the pores of the foam are small, the mechanical properties of the foam can be improved, but the proportion of the foam is large because the plastic substrate is too dense. Whether the foaming pore size is average Evenly, it affects the consistency and reproducibility of its mechanical properties. If the pore size is not uniform, it is easy to influence the test results because the pore size of the foam used in each mechanical property test is inconsistent. For the user, the midsole made of the foam with uneven pore size may cause unevenness due to the different compression variables of the midsole of the shoe, which may cause damage to the foot.

Therefore, when a midsole is made of a foam composition of a polyolefin as a plastic substrate, how to achieve a balance between mechanical properties such as density, hardness, and pressure resistance has been the focus of the footwear industry. .

The foaming method of the conventional polyolefin foam can be simply divided into two types. The first foaming method is a batch mixing method, which includes steps of low temperature refining, rolling, foaming, molding, etc., low temperature refining refers to The plastic substrate is melted and uniformly mixed with other components at a temperature at which the foaming agent is not chemically foamed and the bridging agent does not cause a crosslinking reaction. Pressing the sheet means pressing the mixture which has undergone the low-temperature refining. Flake, foaming means applying appropriate temperature and pressure to the sheet to melt the plastic substrate, and causing the bridging agent and the foaming agent to act, so that the original sheet forms a foamed slab, and the molding means The slabs are cut to make the final product. The second foaming method is injection foam molding, and includes steps of low temperature kneading, extrusion granulation, and injection foam molding. Regardless of the method used, the properties of the polyolefin foam are closely related to the formulation of the composition, and the amounts and types of the components used affect each other and are pinned, resulting in differences in the physical properties of the foam.

Conventional polyolefin foam compositions generally contain a plastic substrate such as EVA, a bridging agent, a blowing agent, and various additives such as fillers, colorants, slip agents, and the like. The bridging agent acts to crosslink between different chains of the chain polymer of the plastic substrate, and becomes a network structure, which can Increasing the strength and elasticity of the plastic substrate, and improving the mechanical properties of the resulting foam, also plays an important role in the foaming process, by increasing the strength and elasticity of the foamed plastic substrate to make the foamed plastic substrate The pore structure can catch the gas generated by the foaming agent, so that the gas is not easily dissipated, and the pore structure can be maintained without defoaming reaction due to collapse. The foaming agent acts to foam at a specific temperature. In the reaction, usually the blowing agent decomposes to generate a gas, which causes the plastic substrate to have a pore structure and causes the volume of the plastic substrate to expand. Other additives can be used to improve the appearance and properties of the foam, such as the function of the filler. In order to reduce the cost and increase the hardness and prevent the shrinkage, the coloring material can impart the color of the foam, and on the one hand, the sliding agent can make the plastic substrate less likely to stick to the production equipment, and on the other hand, the surface of the foam can be smooth and beautiful. The amount and type of each component may be mutually inhibited to affect the properties of the foam. For example, when the amount of the foaming agent is increased, the pores of the foam become large and pores of uneven size are easily formed due to rapid expansion. However, by increasing the bridging agent or increasing the filler, the hardness of the plastic substrate can be increased to limit the speed of the pore expansion, thereby limiting the size of the pores. Therefore, on the practical level, it is difficult for us to separate one of the components separately and explore its effect on the foam. Even if the components of the foam composition are the same, as long as there is a difference in the amount of the package, Will cause the final foam physical properties to be different.

Through our painstaking research and many experiments, we finally get a formula of polyolefin foam composition that can take into consideration the density and mechanical properties. We will not disclose the experimental results of our painstaking research to the world. The manufacturer creates a shoe midsole with superior physical properties.

The object of the present invention is to provide a polyolefin foam composition, and the foam obtained by using the polyolefin foam composition can achieve both density and mechanical properties. Sex, so it is very suitable for making shoe midsole. The shoe midsole made of the conventional polyolefin foam composition has a specific gravity of 0.2 g per cubic centimeter to 0.24 g per cubic centimeter. The shoe midsole made of the polyolefin foam composition of the present invention can maintain a mechanical property, and the specific gravity is less than or equal to 0.15 g per cubic centimeter, which is at least compared with the proportion of the midsole of the conventional shoe. The reduction of 25 weight percentages can maintain the general physical properties of the midsole of the shoe, effectively achieving the goal of balancing lightweight and qualified mechanical properties.

One aspect of the present invention provides a polyolefin foam composition comprising an ethylene/vinyl acetate copolymer (EVA) and a polyolefin elastomer (Polyolefin Elastomers, abbreviated as POE), EVA and POE. The weight ratio relationship ranges from: EVA to POE is 40 to 60 to EVA, and POE is 70 to 30. The weight of the plastic substrate EVA and POE is regarded as 100 parts by weight, and the other 2 to 12 parts by weight of nanofill is included. The agent, 0.4 to 1.4 parts by weight of a bridging agent, 2.0 to 4.0 parts by weight of a foaming agent, and 1.0 to 2.0 parts by weight of a nanofoaming aid.

The POE may be selected from a grade of 88 to 95 degree A grade pellets available from Engage 8480, Engage 8540 or Engage 8200 manufactured by the Dow Chemical Company.

The purpose of the nanofiller is to form a fine foamed structure of the foam, and it is possible to reduce cost and increase hardness. A nanometer calcium carbonate having an average particle diameter of 200 nm to 300 nm or a nano talc powder having an average particle diameter of 200 nm to 300 nm can be selected. When the conventional technology uses calcium carbonate or talc as a filler for the polyolefin foam composition, the particle size used ranges from 5 micrometers to 50 micrometers. In the present invention, the filler is nano-sized to be sufficiently mixed with other components, and can be more uniformly dispersed in the foam made of the composition, so that the foam can be exhibited. Consistent, average hardness.

The bridging agent acts to crosslink different chains of the chain polymer of the plastic substrate to form a network structure, which can strengthen the elasticity and hardness of the plastic substrate, and can fix the pore shape, maintain the pore structure, and avoid Defoaming, the following factors should be considered when selecting the bridging agent: (1) high crosslinking efficiency and good dispersibility, (2) suitable decomposition temperature and speed, stable temperature at low temperature mixing, no premature Cross-linking phenomenon or a large amount of volatiles, (3) the decomposition agent of the bridging agent is non-toxic and tasteless, (4) the bridging agent does not react chemically with other components. A polyolefin foam composition according to an embodiment of the present invention, wherein the bridging agent may be dicumyl peroxide.

The foaming agent generates a foaming reaction at a suitable temperature, decomposes to generate a gas, and the plastic substrate expands due to the generation of pores, and the foaming aid is used to lower the temperature at which the foaming agent generates a foaming reaction, thereby making it The polyolefin foam composition can be reacted according to an embodiment of the present invention, wherein the foaming agent can be azomethicin, and the nano foaming aid can be an average. Nano zinc oxide having a particle diameter of 160 nm to 220 nm. The use of zinc oxide as a foaming aid can reduce the temperature at which azomethicin can cause a foaming reaction from about 190 ° C to 220 ° C to about 150 ° C to 170 ° C. The particle size of the foaming aid has a decisive influence on the foaming reaction. If a foaming aid of the same quality but different particle diameter is added, the larger the particle size, the slower the reaction rate, the less easily the pore formation is synchronized, that is, Some of the pores are forming and some of the pores collapse due to defoaming, which in turn causes the pore size to vary. In the invention, the zinc oxide of the foaming assistant is nanometerized, and the zinc oxide particles are reduced, and on the other hand, the zinc oxide particles are enlarged. The surface area accelerates the reaction rate, so that the plastic substrate can be foamed simultaneously and rapidly, and the pore size is maintained and controlled by an appropriate proportion of the bridging agent, so that the foam produced by the invention has smaller pores and a larger number of pores. More and the pore size is more uniform. On the other hand, since the foaming aid particles become smaller, it is easier to uniformly disperse in the plastic substrate to make the foaming reaction more uniform.

The polyolefin foam composition may be added with at least one additive in addition to the above components to improve the properties of the foam produced. The additive may be a compatibilizer, a slip agent, a tackifier or the like. The combination. The role of the compatibilizer is to improve the poor compatibility of two or more polymers when blended. A polyolefin foam composition according to an embodiment of the present invention, wherein the compatibilizing agent may be selected from a maleic anhydride grafted POE (MA grafted POE), and the slip agent may be monostearic acid.

Another aspect of the present invention provides a shoe midsole obtained by foam molding of the above polyolefin foam composition. The foam molding method can adopt a more conventional batch mixing method, for example, batching all components into a banbury mixer, a kneader mixer or other mixing device to make all the components. Mixing evenly, and then using a machine such as a tworoll mill to form a mixture of the kneaded mixture, placing the sheet into a flat-plate mold, and crosslinking and foaming at a certain temperature and pressure to form a thick sheet. The slab is then cut as needed. Newer technologies such as injection foam molding can also be used. All components are firstly mixed at a low temperature to form rubber pellets, and the rubber pellets are melted and shot to form a foam molding. The above methods are well known in the industry and will not be described in detail herein.

A midsole according to an embodiment of this aspect of the invention has a specific gravity of from 0.14 grams per cubic centimeter to 0.15 grams per cubic centimeter.

A midsole according to another embodiment of this aspect of the invention has a specific gravity of from 0.12 grams per cubic centimeter to 0.14 grams per cubic centimeter.

The polyolefin foam composition of the present invention is subjected to a reproducible experimental result to obtain a preferable ratio relationship between the components, and then the filler and the foaming aid are nano-sized, in addition to foaming the polyolefin. The midsole of the shoe made of the body composition has an average hardness which is increased on average, and has a small size, a uniform size, and a large number of pores. Because the pores are small and more, the plastic substrate between the pores and the pores has the function of supporting and protecting the pores, so that the midsole of the shoe is not easily deformed by the extrusion of external force, so the shoe is penetrated through the dense pore structure. The bottom has good hardness and elasticity. If the number of stomata is large, the proportion of the midsole of the shoe is small, and the uniform size of the stomata makes the entire midsole of the shoe exhibit consistent physical properties.

Comparative example:

Please refer to FIG. 1 , which is a shoe midsole which is foam molded by using a conventional polyolefin foam composition, and is observed by an optical microscope at a magnification of 50 times, and then the cross section is enlarged by a charge coupled device (CCD). photo. The lighter part is the pores, and the darker part between the pores and the pores is the plastic substrate. The inner diameters of the pores of the pores 0, the pores 1, the pores 2, the pores 3, the pores 4, the pores 5, the pores 6, the pores 7, the pores 8, and the pores 9 are respectively measured, and the arrows represent the direction of the measured inner diameter of the pores, and the results are obtained. Listed in Table 1.

The polyolefin foam composition used in the midsole of the shoe is formulated as follows: the plastic substrate is ethylene/vinyl acetate copolymer (EVA) and polyolefin. The ratio of the weight ratio of the elastomer (POE), EVA to POE is: EVA is 40 to 60 to 60 to 60 to EVA, and 70 to 30 is POE. The weight of the plastic substrate EVA and POE is regarded as 100 parts by weight, and 10 is included. To 23 parts by weight of the filler, 0.4 to 1.4 parts by weight of the bridging agent, 1.5 to 4 parts by weight of the blowing agent, and 0.5 to 1.2 parts by weight of the lubricant.

Among them, the POE may be selected from a grade of 88 to 95 degree A grade pellets available from Engage 8480, Engage 8540 or Engage 8200 manufactured by the Dow Chemical Company. The filler is calcium carbonate, clay or talc powder having an average particle diameter of 5 to 50 μm, dicumyl oxide is used as a bridging agent, stearic acid is used as a foaming agent, and stearic acid is used as a slip agent.

All the ingredients of the above formula were batched into a banbury mixer, all the ingredients were uniformly mixed, and the kneaded mixture was sliced using a tworoll mill, and the sheet was placed in a flat plate mold. The cross-linking foaming is carried out at a temperature of 150 ° C to 180 ° C and a pressure of 150 kg / cm ² , and the foaming time is adjusted according to the thickness of the above-mentioned sheet, and the thickness of the mold is multiplied by 1.6 times, that is, required The foaming time, the unit of the thickness of the mold is mm (mm), and the unit of time is minute (min). After the above-mentioned sheet is foamed, it is cut to form a midsole.

The midsole of the foamed foamed polyolefin foam composition has a specific gravity of 0.2 g per cubic centimeter to 0.24 g per cubic centimeter.

Please refer to Table 1, which is the number of the air holes in the first figure and the inner diameter of the air holes corresponding to the number. It can be seen from Table 1 that the average inner diameter of the pores is 98.75 um.

First embodiment:

Referring to FIG. 2, the midsole of the foamed foamed polyolefin foam composition according to the first embodiment of the present invention is enlarged by an optical microscope at a magnification of 50, and the cross section is coupled by a charge coupled device ( CCD) Take a magnified photo taken. The lighter part is the pores, and the darker part between the pores and the pores is the plastic substrate. The inner diameters of the pores of the pores 0, the pores 1, the pores 2, the pores 3, the pores 4, the pores 5, the pores 6, the pores 7, the pores 8, and the pores 9 are respectively measured, and the arrows represent the direction of the measured inner diameter of the pores, and the results are obtained. Listed in Table 2.

The polyolefin foam composition used in the midsole of the shoe is formulated as follows: the plastic substrate component is ethylene/vinyl acetate copolymer (EVA) and polyolefin elastomer (POE), and the weight ratio range of EVA and POE The ratio of EVA to POE is 40 to 60 to EVA, and the POE is 70 to 30. The weight of the plastic substrate EVA and POE is regarded as 100 parts by weight, and the other is 5 to 9 parts by weight of nano filler, 0.4 to 1.4. Weight part of bridging agent, 2.4 to 2.9 parts by weight of foaming agent, 1.2 to 1.5 parts by weight of nano foaming aid, 11.2 parts by weight of compatibilizer, 1.2 parts by weight of slipper, 2.8 parts by weight of tackifier Agent.

Among them, the POE may be selected from a grade of 88 to 95 degree A grade pellets available from Engage 8480, Engage 8540 or Engage 8200 manufactured by the Dow Chemical Company. The nanofiller uses a nanometer calcium carbonate having an average particle diameter of 200 nm to 300 nm, a nanometer clay having an average particle diameter of 200 nm to 300 nm or an average particle diameter of 200 nm to 300 nm. Nano talcum powder, bridging agent using dicumyl oxide, foaming agent using azodimethylamine, nano foaming aid using a nanometer zinc oxide with an average particle diameter of 160 nm to 220 nm. The solvent used maleic anhydride grafted POE and the slip agent used stearic acid.

All the ingredients of the above formula were batched into a banbury mixer, all the ingredients were uniformly mixed, and the kneaded mixture was sliced using a tworoll mill, and the sheet was placed in a flat plate mold. The cross-linking foaming is carried out at a temperature of 150 ° C to 180 ° C and a pressure of 150 kg / cm ² , and the foaming time is adjusted according to the thickness of the above-mentioned sheet, and the thickness of the mold is multiplied by 1.6 times, that is, required The foaming time, the unit of the thickness of the mold is mm (mm), and the unit of time is minute (min). After the above-mentioned sheet is foamed, it is cut to form a midsole.

The midsole of the foamed foamed polyolefin foam composition has a specific gravity of 0.14 g per cubic centimeter to 0.15 g per cubic centimeter, which is less than 0.2 g per cubic centimeter of the base of the conventional shoe to 0.24 g per cubic centimeter.

Please refer to Table 2, which is the figure of the air hole and the inner diameter of the air hole corresponding to the number in the second figure (rounded to the second place after the decimal point). It can be seen from Table 2 that the average inner diameter of the pores is 65.29 um, which is smaller than the average inner diameter of the pores of the conventional shoe midsole of Table 1 of 98.75 um.

Second embodiment:

Please refer to FIG. 3 , which is a foamed and formed midsole of a polyolefin foam composition according to a second embodiment of the present invention, which is observed by an optical microscope at a magnification of 50 times, and then the cross section is a charge coupled device ( CCD) Take a magnified photo taken. The lighter part is the pores, and the darker part between the pores and the pores is the plastic substrate. The inner diameters of the pores of the pores 0, the pores 1, the pores 2, the pores 3, the pores 4, the pores 5, the pores 6, the pores 7, the pores 8, and the pores 9 are respectively measured, and the arrows represent the direction of the measured inner diameter of the pores, and the results are obtained. Listed in Table 3.

The polyolefin foam composition used in the midsole of the shoe is as follows: the plastic substrate component is ethylene/vinyl acetate copolymer (EVA) and polyolefin elastomer (POE), and the weight ratio of EVA to POE ranges from: The EVA has a POE of 40 to 60 to EVA and a POE of 70 to 30, and the weight of the plastic substrate EVA and POE is regarded as 100 parts by weight, and further comprises 8 to 11.2 parts by weight of the nano filler, 0.4 to 1.4 parts by weight. The bridging agent, 2.6 to 3.2 parts by weight of the foaming agent, 1.3 to 1.6 parts by weight of the nanofoaming aid, 11.2 parts by weight of the compatibilizer, 1.2 parts by weight of the slip agent, and 2.8 parts by weight of the tackifier.

Among them, the POE may be selected from a grade of 88 to 95 degree A grade pellets available from Engage 8480, Engage 8540 or Engage 8200 manufactured by the Dow Chemical Company. The nanofiller uses a nanometer calcium carbonate having an average particle diameter of 200 nm to 300 nm, a nanometer clay having an average particle diameter of 200 nm to 300 nm or an average particle diameter of 200 nm to 300 nm. Nano talc powder, bridging agent using dicumyl oxide, foaming agent using azo dimethyl hydrazine, nano foaming auxiliaries using a nanometer oxidation with an average particle diameter of 160 nm to 220 nm Zinc, a compatibilizer, uses maleic anhydride grafted POE, and a slip agent uses stearic acid.

All the ingredients of the above formula were batched into a banbury mixer, all the ingredients were uniformly mixed, and the kneaded mixture was sliced using a tworoll mill, and the sheet was placed in a flat plate mold. The cross-linking foaming is carried out at a temperature of 150 ° C to 180 ° C and a pressure of 150 kg / cm ² , and the foaming time is adjusted according to the thickness of the above-mentioned sheet, and the thickness of the mold is multiplied by 1.6 times, that is, required The foaming time, the unit of the thickness of the mold is mm (mm), and the unit of time is minute (min). After the above-mentioned sheet is foamed, it is cut to form a midsole.

The midsole of the foamed foamed polyolefin foam composition has a specific gravity of 0.12 g per cubic centimeter to 0.14 g per cubic centimeter, which is less than 0.2 g per cubic centimeter of the base of the conventional shoe to 0.24 g per cubic centimeter. .

Please refer to Table 3, which is the figure of the air hole and the inner diameter of the air hole corresponding to the number in the third figure (rounded to the second place after the decimal point). It can be seen from Table 3 that the average inner diameter of the pores is 48.19 um, which is at least 50% lower than the average inner diameter of the pores of the conventional shoe in Table 1 of 98.75 um.

Please refer to Table 4, which is a test result obtained by testing the specific gravity and various mechanical properties of the midsole of the foamed foamed polyolefin composition of the second embodiment. The first column is the type of physical property, and the second column is the test method. Among them, ASTM (American Standard of Testing Materials) refers to the American Society for Measurement Standards, and ASTM D2240 is taken as an example to indicate the test method using American Society for Measurement Standards No. D2240. A test method has standard procedures, which are described on the official website of the American Society for Measurement Standards. It is not described here. The third column is the test result, and the fourth column is the physical demand for the midsole of the shoe. Research and development goals.

Comparing the first to third figures, and comparing the data of Tables 1 to 3, it can be seen that the inner diameter of the foamed midsole of the shoe according to the present invention is significantly smaller than the inner diameter of the conventional air hole, and the inner diameter of the air hole is evenly distributed. . From the test results of Table 4, it is shown that the density of the midsole of the foamed molded shoe of the present invention is much smaller than the density of the midsole of the conventional shoe, but other mechanical properties can meet the expectations and needs of the manufacturer. When the polyolefin foam composition is applied to the midsole of the shoe, an excellent midsole having a balance of various physical properties such as density, hardness, and pressure resistance can be obtained.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention can be modified and modified without departing from the spirit and scope of the present invention. The scope is subject to the definition of the scope of the patent application attached.

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The above and other objects, features, advantages and embodiments of the present invention will become more <RTIgt; <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; The cross section of the cross section was observed by an optical microscope at a magnification of 50, and the enlarged photograph taken by a charge coupled device (CCD) was taken.

Fig. 2 is a midsole of a foamed molding of a polyolefin foam composition according to a first embodiment of the present invention, which is observed by an optical microscope at a magnification of 50 times, and then the cross section is photographed by a charge coupled device (CCD). Enlarge the photo.

Fig. 3 is a view showing a foamed molded midsole of a polyolefin foam composition according to a second embodiment of the present invention, which is observed by an optical microscope at a magnification of 50 times, and then the cross section is photographed by a charge coupled device (CCD). Put Big photo.

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Claims (10)

A polyolefin foam composition for a midsole comprising: (A) an ethylene/vinyl acetate copolymer (EVA); (B) a polyolefin elastomer (POE); (C) a nanofiller; a bridging agent; (E) a foaming agent; and (F) a nanofoaming auxiliaries; the ratio of each component is as follows, wherein the weight ratio (A)/(B) of the component (A) to the component (B) is 40 /60 to 70/30, based on 100 parts by weight of the (A) component and (B) component, the content of the component (C) is 2 to 12 parts by weight, and the content of the component (D) is 0.4 to 1.4 parts by weight, ( E) The content of the component is 2.0 to 4.0 parts by weight, and the content of the component (F) is 1.0 to 2.0 parts by weight. The polyolefin foam composition of the shoe midsole according to claim 1, further comprising at least one additive. The polyolefin foam composition of the shoe midsole according to claim 1, wherein the nanofiller is a nanometer calcium carbonate. The polyolefin foam composition of the shoe midsole according to claim 1, wherein the nanofiller is a nano talc powder. The polyolefin foam composition of the midsole of the shoe of claim 1 And wherein the nano filler has an average particle diameter of from 200 nm to 300 nm. The polyolefin foam composition of the shoe midsole according to claim 1, wherein the nanofoaming aid is one nano zinc oxide. The polyolefin foam composition of the shoe midsole according to claim 6, wherein the nano zinc oxide has an average particle diameter of from 160 nm to 220 nm. A shoe midsole obtained by foam molding of a polyolefin foam composition of a shoe midsole according to any one of claims 1 to 7. The shoe midsole according to claim 8 has a specific gravity of 0.14 g per cubic centimeter to 0.15 g per cubic centimeter. The midsole of the shoe of claim 8 having a specific gravity of from 0.12 grams per cubic centimeter to 0.14 grams per cubic centimeter.