JP2001031790A - Thermoplastic polyurethane injected and foamed molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thermoplastic polyurethane injected foamed molding having uniform cells, excellent external appearance and furthermore, excellent performances of a thermoplastic polyurethane such as flexibility, mechanical characteristics, abrasion resistance, flaw resistance, impact absorption, and oil resistance by an environmentally friendly method. SOLUTION: Injection foaming molded products which excel in flexibility, mechanical characteristics, abrasion resistance, mar resistance, impact absorption, oil resistance and the like can be obtained by subjecting an expandable thermoplastic polyurethane composition obtained by compounding 100 pts.wt. thermoplastic polyurethane having an inherent viscosity of 0.7-2.0 with 2-20 pts.wt. alkyl (meth)acrylate based polymer having a number average molecular weight of 1,500,000-6,000,000 and 0.5-10 pts.wt. organic thermally decomposable blowing agent having a decomposition temperature of 120-220 deg.C to injection foaming.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection-molded thermoplastic polyurethane product obtained by mixing a thermoplastic polyurethane with a specific alkyl (meth) acrylate polymer and a foaming agent, and subjecting the mixture to injection foaming. About. The thermoplastic polyurethane injection foamed product provided by the present invention is excellent in abrasion resistance, scratch resistance, shock absorption and the like, and has a low specific gravity, so that a lightweight molded product, a cushioning material, a cushioning material,
In addition to soles and various grips, it is useful for applications such as mobile phones, portable audio devices, mobile computers, and handy terminals.

[0002]

2. Description of the Related Art Conventionally, thermoplastic polyurethane has many characteristics such as high elastic modulus and excellent abrasion resistance and oil resistance, and thus has been attracting attention as an alternative material to rubber and plastics. As a molding material to which a general plastic molding method can be applied, it has been used in a wide range of applications.

In recent years, in addition to shoe soles, various grips, etc., mobile phones, stereos with headphones, portable CDs
Portable devices such as players, portable MD players, mobile computers, and handy terminals are on the rise, and there is a demand for increased portability and protection of the housing and internal devices. In order to protect the housings and internal devices of these products, various elastomer materials are being used as coating materials for the products. The performance required of these coating materials is lightweight, abrasion resistance, scratch resistance, impact absorption, and the like, and a thermoplastic polyurethane material having these physical properties is suitable.

By the way, as a conventional method for producing a polyurethane foam, (1) water is added to a polyurethane raw material, and carbon dioxide gas is generated by a reaction between the isocyanate component in the raw material and water to form and foam the polyurethane. (2) a method of adding a fluorine-based expanding agent such as Freon gas to a raw material for polyurethane to form and foam polyurethane to produce a polyurethane foam.

However, in the above-mentioned conventional methods (1) and (2), since a raw material is used, the procurement (transportation and
There are many problems such as complexity of storage) and contamination of the working environment. In addition, all of these production methods are suitable for thermosetting resins, and are difficult to apply to the production of thermoplastic polyurethane foams. Another drawback is that it is difficult to recycle. Furthermore, in the conventional method (2),
There is also a problem that a fluorine-based expanding agent such as chlorofluorocarbon gas whose use has been regulated in recent years in view of destruction of the global environment is used.

In addition, there is a problem in applying the method for producing a foam of a thermoplastic resin such as polyvinyl chloride, polyethylene, polypropylene, polystyrene, EVA and ABS to the injection molding of foamed polyurethane as it is. For example,
There is a method for producing a foam by adding a pyrolytic foaming agent to the resin, heating and melting the resin, and decomposing the foaming agent to generate gas. However, since this production method is mainly used for extrusion foam molding, when polyurethane is injection foam molded using a general-purpose injection molding machine, the viscosity of the polyurethane at the time of melting is large, so that it cannot be molded in a stable state. Alternatively, there is a problem that a good injection foamed molded product cannot be obtained due to poor appearance or sink marks.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide uniform air bubbles and excellent appearance without using chlorofluorocarbon or organic solvents which are problematic in terms of environment and safety. Another object of the present invention is to provide an injection-molded thermoplastic polyurethane foam which retains excellent properties such as flexibility, mechanical properties, abrasion resistance and oil resistance of the thermoplastic polyurethane.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above-mentioned object, and as a result, have found that when a pyrolytic foaming agent is added to thermoplastic polyurethane to produce an injection foamed molded product. Instead of using a thermoplastic polyurethane alone, a thermoplastic polyurethane having a specific viscosity is blended with a (meth) acrylic acid alkyl ester-based polymer having a specific range of 1.5 to 6,000,000 in number average molecular weight. As a result, the viscosity becomes extremely suitable for injection foam molding, the gas generated by the thermal decomposition of the foaming agent is sufficiently and uniformly retained in the melt without unevenness, and fine and uniform bubbles are formed in the foam. The present inventors have found that a polyurethane injection foam having a uniform appearance and a good external appearance can be obtained, and completed the present invention.

That is, according to the present invention, the logarithmic viscosity is 0.7 to
A thermoplastic polyurethane composition comprising 100 parts by weight of 2.0 dl / g thermoplastic polyurethane and 2 to 20 parts by weight of a (meth) acrylic acid alkyl ester-based polymer having a number average molecular weight of 1.5 to 6 million. The present invention relates to an injection foam molded article.

In a preferred embodiment, the molded article of the present invention has a taper abrasion loss of 70 mg or less. Also,
In a preferred embodiment, a skin layer is formed on the surface of the molded product of the present invention.

The present invention also relates to a portable device housing having the above-mentioned molded product on the outermost surface. Furthermore, the present invention relates to a shoe sole comprising the above-mentioned molded product.

Further, the present invention provides that the logarithmic viscosity is 0.7 to 0.7.
2 to 20 parts by weight of a (meth) acrylic acid alkyl ester-based polymer having a number average molecular weight of 1.5 to 6 million per 100 parts by weight of 2.0 dl / g thermoplastic polyurethane,
And a method for producing an injection foamed molded article comprising a thermoplastic polyurethane composition, wherein 0.5 to 10 parts by weight of an organic thermal decomposition type foaming agent having a decomposition temperature of 120 to 220 ° C is blended and injection foamed. .

[0013]

DETAILED DESCRIPTION OF THE INVENTION The logarithmic viscosity of the thermoplastic polyurethane used in the present invention must be about 0.7 to 2.0 dl / g, and about 0.8 to 1.8 dl / g. Is preferred. When a thermoplastic polyurethane having such a logarithmic viscosity is used, a thermoplastic polyurethane composition suitable for foaming can be obtained, and a foam having more excellent properties such as mechanical properties and abrasion resistance can be obtained.

The logarithmic viscosity of the thermoplastic polyurethane referred to in the present specification is such that an N, N-dimethylformamide solution containing n-butylamine at a ratio of 0.05 mol / liter has a concentration of 0.5 g of the thermoplastic polyurethane. / Dl, and the flow time of the thermoplastic polyurethane solution at a temperature of 30 ° C. was measured using an Ubbelohde viscometer, and was determined by the following equation.

Logarithmic viscosity of thermoplastic polyurethane = ｛ln
(T / to)｝ / c [where, t is the flow time of the thermoplastic polyurethane solution (second), to is the flow time of the solvent (second),
And c is the concentration of the thermoplastic polyurethane solution (g / d
1) is shown. ]

The thermoplastic polyurethane used in the present invention has a logarithmic viscosity of about 0.7 to 2.0 dl / g, and any thermoplastic polyurethane which can be melted by heating can be used. Among them, polymer diols,
A thermoplastic polyurethane obtained by reacting an organic diisocyanate and a chain extender and having a logarithmic viscosity of about 0.7 to 2.0 dl / g is preferred.

If the logarithmic viscosity is less than 0.7, the mechanical properties of the thermoplastic polyurethane are low, and the abrasion resistance is poor. When the logarithmic viscosity exceeds 2.0 dl / g,
The melt viscosity of the thermoplastic polyurethane becomes too high, foaming is suppressed at the time of injection foam molding, it is difficult to form fine bubbles, and the distribution of the bubbles tends to be uneven. Also,
Dispersion of the additive is also likely to be uneven, which is not preferable.

The high molecular weight diol used for producing the thermoplastic polyurethane has a number average molecular weight of 800 to 8,
000 is preferable, and 900 to 6,000 is more preferable. When the high molecular weight diol having such a number average molecular weight is used, the mechanical strength of the thermoplastic polyurethane obtained is further improved, and the mechanical strength of the foam of the present invention is further improved. The number average molecular weight of the high molecular weight diol referred to in this specification is JIS K15.
It means the number average molecular weight calculated based on the hydroxyl value measured according to 77.

Examples of the polymer diol constituting the thermoplastic polyurethane include polyester diol, polyether diol, polycarbonate diol, polyester polycarbonate diol, and polyester polyether diol. They are,
They may be used alone or in combination of two or more.

The polyester diol is prepared, for example, by subjecting a dicarboxylic acid component composed of an ester-forming derivative such as a dicarboxylic acid, an ester or an anhydride thereof to a low-molecular diol component by a direct esterification reaction or transesterification reaction according to a conventional method. Can be manufactured.

Examples of the dicarboxylic acid component used for producing the polyester diol include glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 2-methylsuccinic acid,
2-methyladipic acid, 3-methyladipic acid, 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-
Aliphatic dicarboxylic acids having 5 to 12 carbon atoms such as dimethyldecanedioic acid and 3,7-dimethyldecandioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and orthophthalic acid; and ester-forming derivatives thereof. Can be mentioned. These dicarboxylic acid components may be used alone or in combination of two or more. Among them, as the dicarboxylic acid component, aliphatic dicarboxylic acids having 5 to 12 carbon atoms are preferably used from the viewpoint of excellent flexibility and mechanical properties of the obtained foam, and in particular, adipic acid, azelaic acid, sebacic acid Is more preferably used.

Examples of the low molecular weight diol component used for producing the polyester diol include ethylene glycol, 1,3-propanediol, and 2-methyl-1,3.
-Propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl -1,
8-octanediol, 1,9-nonanediol, 1,
Aliphatic diols such as 10-decanediol; alicyclic diols such as cyclohexanedimethanol and cyclohexanediol; These low molecular diol components may be used alone or in combination of two or more. Among them, 3-methyl-1,5-
A low molecular weight diol component having a pentanediol content of 50 mol% or more is preferably used because the resulting foam has good flexibility and rebound resilience.

As the polyether diol, for example,
Polyethylene glycol, polypropylene glycol,
Examples thereof include polytetramethylene glycol. These polyether diols may be used alone or in combination of two or more. Among them, polytetramethylene glycol is preferably used because the resulting foam has good flexibility and hydrolysis resistance.

As the polycarbonate diol, for example, a low molecular diol component, a dialkyl carbonate,
Examples thereof include a polycarbonate diol obtained by a reaction with a carbonate compound such as an alkylene carbonate and a diaryl carbonate.

As the low molecular diol component used for producing the polycarbonate diol, the low molecular diol component used for producing the above polyester diol is used. Examples of the dialkyl carbonate that reacts with the low molecular weight diol component include dimethyl carbonate and diethyl carbonate, examples of the alkylene carbonate include ethylene carbonate, and examples of the diaryl carbonate include diphenyl carbonate.

As the polyester polycarbonate diol, for example, a polyester polycarbonate diol obtained by simultaneously reacting the low molecular diol component, the dicarboxylic acid component and the carbonate compound; a polyester diol and a polycarbonate diol synthesized in advance, and a carbonate compound And a polyester polycarbonate diol obtained by reacting with a diol component and / or a dicarboxylic acid component.

The type of the organic diisocyanate used for producing the thermoplastic polyurethane is not particularly limited, and any organic diisocyanate conventionally used for producing the thermoplastic polyurethane can be used. Among them,
One or more of aromatic diisocyanate, alicyclic diisocyanate and aliphatic diisocyanate having a molecular weight of 500 or less are preferably used.

Examples of organic diisocyanates include 4,
4′-diphenylmethane diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate,
Hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and the like can be mentioned. These organic diisocyanates may be used alone,
It may be used in combination of more than one kind. Among them, 4,4'-
Diphenylmethane diisocyanate is preferably used because the resulting foam has good mechanical properties.

The type of the chain extender used for producing the thermoplastic polyurethane is not particularly limited, and any chain extender conventionally used for producing the thermoplastic polyurethane can be used. Among them, as the chain extender, a low molecular weight compound having a molecular weight of 300 or less and having two or more active hydrogen atoms capable of reacting with an isocyanate group in a molecule is preferably used. Examples of such chain extenders include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-
Examples thereof include diols such as 1,5-pentanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, bis- (β-hydroxyethyl) terephthalate, and 1,9-nonanediol. Can be These chain extenders may be used alone,
It may be used in combination of more than one kind. Among them, carbon number 2
Ten aliphatic diols are preferably used from the viewpoint of good mechanical properties of the foam, and 1,4-butanediol is more preferably used.

The thermoplastic polyurethane can be obtained by reacting the above-mentioned polymer diol, organic diisocyanate and chain extender, but the production method thereof is not particularly limited, and other components may be used as required in addition to the above three components. However, it can be produced by a prepolymer method or a one-shot method using a urethanation reaction technique appropriately used by those skilled in the art. Among them, a method of melt polymerization substantially in the absence of a solvent,
In particular, a method of performing continuous melt polymerization using a multi-screw extruder is preferably used.

As the thermoplastic polyurethane, those having a hardness (JIS-A hardness) of 55 to 95 are preferably used, and those having a hardness of 60 to 90 are more preferable.
It is preferable to use a thermoplastic polyurethane having such a hardness because a foam having excellent mechanical strength and flexibility can be obtained.

In the present invention, an alkyl (meth) acrylate polymer having a number average molecular weight of 1.5 to 6,000,000 is used. If the number average molecular weight is less than 1.5 million, the melt viscosity of the foamable polyurethane composition will not be suitable for holding bubbles, and foaming will be coarsened or burst, and fine bubbles of uniform size will occur. It is not possible to form a foam in which the particles are distributed without unevenness, and furthermore, the appearance of the foam tends to be poor due to the occurrence of uneven patterns and sink marks on the surface of the foam. Conversely, when the number average molecular weight exceeds 6,000,000, not only dispersibility in the thermoplastic polyurethane becomes poor, but also melt viscosity becomes high and moldability deteriorates, and foamability also deteriorates.

The number average molecular weight of the (meth) acrylic acid alkyl ester polymer is 1.5 to 6,000,000.
It is preferably from 500,000 to 5,000,000, more preferably from 3,000,000 to 5,000,000. Further, among (meth) acrylic acid alkyl ester-based polymers, those mainly composed of alkyl acrylate and alkyl methacrylate having 1 to 10 carbon atoms in the alkyl group forming the ester are most preferably used. .

Preferred examples of the alkyl (meth) acrylate constituting the alkyl (meth) acrylate-based polymer used in the present invention include methyl acrylate, ethyl acrylate, n-propyl acrylate, and isopropyl acrylate. Alkyl acrylates such as butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, methacrylic acid And methacrylic acid alkyl esters such as -2-ethylhexyl.
The (meth) acrylic acid alkyl ester-based polymer may be formed from one kind of (meth) acrylic acid alkyl ester, or may be formed from two or more kinds. Among them, it is preferable to use a copolymer mainly composed of methyl methacrylate and butyl acrylate.

The alkyl (meth) acrylate-based polymer used in the present invention may contain, if necessary, a small amount (generally 25 mol% or less) of another copolymer together with the alkyl (meth) acrylate unit. It may have a unit derived from a polymerizable unsaturated monomer. Such copolymerizable unsaturated monomers include, for example, ethylene,
Butadiene, isoprene, styrene, α-methylstyrene, acrylonitrile and the like can be mentioned. The (meth) acrylic acid alkyl ester-based polymer may have a unit composed of one or two of these copolymerizable unsaturated monomers.

In the present invention, it is necessary to contain 2 to 20 parts by weight of the alkyl (meth) acrylate polymer based on 100 parts by weight of the thermoplastic polyurethane, and 3 to 15 parts by weight. Is preferred. When the use ratio is less than 2 parts by weight, the melt viscosity of the thermoplastic polyurethane composition is low, the gas generated by the decomposition of the pyrolytic foaming agent cannot be retained well, and the foaming tends to be coarsened. Sinks occur on the body surface and the surface does not become smooth, and conversely, the usage ratio is 20% by weight.
If it exceeds, the melt viscosity at the time of molding becomes too high, the expansion is suppressed, the expansion ratio becomes small, and not only a foam having a desired expansion ratio cannot be obtained, but also the (meth) Poor dispersion of the alkyl acrylate polymer occurs, unmelted bumps are easily generated on the surface of the foam, and physical properties such as abrasion resistance are poor.

The decomposition temperature used in the present invention is 120 to 2
Examples of the organic thermal decomposition type foaming agent at 20 ° C. include azodicarbonamide (decomposition temperature 195 ° C.) and N, N-dinitrosopentamethylenetetramine (decomposition temperature 200).
° C), 4,4-oxybis (benzenesulfonylhydrazide) (decomposition temperature 157 ° C), and the like.
These foaming agents may be used alone or in combination of two or more. Among them, azodicarbonamide which is excellent in handleability, generates a large amount of gas, and has a sharp decomposition temperature is preferable.

When a foaming agent having a decomposition temperature of less than 120 ° C. is used, the foaming agent is decomposed before the thermoplastic polyurethane composition is melted, and a foam having a high expansion ratio cannot be obtained due to outgassing. . On the other hand, when the decomposition temperature of the foaming agent exceeds 220 ° C., the viscosity of the thermoplastic polyurethane composition becomes too low at the decomposition temperature of the foaming agent, so that not only a foaming ratio of high foaming cannot be obtained but also the appearance and shape are deteriorated. If the temperature is lower than 220 ° C. at which the appropriate viscosity of the thermoplastic polyurethane composition is obtained, the foaming agent remains undecomposed and the expansion ratio does not increase.

The amount of the pyrolytic foaming agent added is 0.5 to 10 parts by weight, preferably about 1 to 5 parts by weight, per 100 parts by weight of the thermoplastic polyurethane. The amount of addition may be adjusted according to the specific gravity of the intended foam, the use of the foam, the amount of gas generated from the foaming agent, and the like.

Further, in the present invention, other additives, for example, a cell regulator (such as inorganic fine powder) for forming uniform and fine cells in a foam, a filler, a reinforcing material, a pigment,
One or two of additives such as an antioxidant, an ultraviolet absorber, a plasticizer, an antistatic agent, a hydrolysis inhibitor, a lubricant, and a flame retardant.
More than one species may be added as needed.

In preparing the foamable polyurethane composition for obtaining the thermoplastic polyurethane injection foam molded article of the present invention, the preparation method is not particularly limited. The use of moisture-absorbed thermoplastic polyurethane greatly affects the foaming state and mechanical properties.Therefore, a method of avoiding moisture absorption as much as possible when preparing a thermoplastic polyurethane composition, and the foaming performance of the pyrolytic foaming agent is not lost. Any method can be adopted. For example, mixing may be performed uniformly using a mixer such as a vertical tumbler or a horizontal mixer that is generally used for mixing resin materials.

When injection molding is performed using the foamable polyurethane composition prepared above, thermoplastic polyurethane,
Types of alkyl (meth) acrylate polymers,
The injection molding conditions are as follows: the cylinder temperature is 120-180 ° C. on the hopper side, and 150-200 ° C. on the central part.
℃, nozzle side 150 ~ 210 ℃, nozzle temperature 150
The temperature is preferably set to ~ 210 ° C.

The specific gravity of the obtained injection-molded thermoplastic polyurethane foam is not particularly limited, and varies depending on the raw materials used, particularly the amount and type of the foaming agent. Generally, it is preferable that the specific gravity is about 1 to 0.6. If the specific gravity is less than 0.6, the abrasion resistance tends to be inferior. If it exceeds 1, the object of weight reduction cannot be achieved, which is not preferable.

In most cases, the surface of an injection-foamed molded article of the thermoplastic polyurethane of the present invention obtained by injection-molding the above-mentioned foamable polyurethane composition has irregularities and irregularities due to swelling of bubbles, sink marks and the like on the surface. (A skin layer is formed). Exposure of air bubbles to the surface reduces abrasion resistance, but this feature of the invention is one reason for improving the abrasion resistance of injection molded foams of thermoplastic polyurethane.

The thermoplastic polyurethane injection foamed molded article of the present invention can be used alone or by laminating with other materials to form molded articles such as shoe soles, watch bands, belts, various grips, mobile phones, It is suitably used for a portable audio device, a mobile computer, or a portable device housing such as a handy terminal.

The thermoplastic polyurethane injection foamed article of the present invention and another material are laminated to form a composite product in which the molded article is located on a part of the surface or on the front surface.
The method of compounding is not particularly limited, and examples thereof include a two-color molding method, an insert molding method, a bonding method using a solvent or a binder, and a heat fusion method.

The two-color molding method is a method of molding two kinds of materials by a special molding machine having two cylinders. One molding machine has a two-sided or three-sided mold, and each mold has a mold design for molding each material. Immediately after the primary material is molded and solidified in the first mold, the molded article and the first mold are combined with a second material designed to mold the secondary material.
And the secondary material is injected.

This two-color molding method is mainly suitable for multiple molding of materials having excellent adhesion to each other, and can be performed in a short time.
There are merits such as that various types of materials can be stacked and molded, and the bonding process can be shortened. This method is used for molding, for example, shoe soles, housings for mobile phones, housings for portable MD players, housings for mobile computers, and the like.

The insert molding method is a method of molding two or more types of molding materials, requiring the same number of molding dies as the number of the respective materials, and adding a new material to the molded product one step before and molding. It is. This molding method is also suitable mainly for multiple molding of materials having excellent adhesiveness, and has advantages such as elimination of an adhesive step and good adhesion. This method is used for molding, for example, shoe soles, housings for mobile phones, housings for portable MD players, housings for mobile computers, and the like.

The adhesion or heat fusion method using a solvent or a binder is a commonly used general method. Any material can be used as long as the material to be bonded or bonded can be bonded and fused, and can be used for various purposes, such as shoe sole processing, watch band or belt processing, various grip processing, It is used for partial processing of portable equipment.

[0051]

EXAMPLES The present invention will be described below in more detail with reference to examples and the like, but the present invention is not limited thereto. In the following examples, measurement of various physical properties and evaluation of physical properties of the obtained foam were performed as follows.

(1) The logarithmic viscosity of the thermoplastic polyurethane was measured by the above method.

(2) Hardness of thermoplastic polyurethane Injection molding of thermoplastic polyurethane (cylinder temperature 18
0-210 ° C, mold temperature 30 ° C) and diameter 120mm,
A disk-shaped test piece having a thickness of 2 mm was formed, and two sheets of the test piece were laminated, and the Shore hardness A was measured in accordance with JIS K 7311.

(3) Specific gravity of foam The specific gravity of the foams obtained in Examples and Comparative Examples was measured according to JIS K6767.

(4) Dispersion state of bubbles The cross sections of the foams obtained in the examples and comparative examples were observed with an optical microscope and evaluated as follows. ：: Air bubbles are uniformly dispersed. X: The dispersion state and size of air bubbles are not uniform.

(5) Appearance of foam The surface condition of the foam obtained in each of the examples and comparative examples was visually observed and evaluated as follows. ：: No unevenness or surface roughness due to swelling of bubbles or sink marks on the surface, and the surface has a thin skin layer and is smooth. ×: Irregularities due to swelling of bubbles, sink marks, surface roughness, etc. have occurred on the surface.

(6) Loss of Taber abrasion loss of resin Injection molding of the composition excluding the foaming agent (cylinder temperature 18
0-210 ° C, mold temperature 30 ° C) and diameter 120mm,
A 2 mm-thick disk-shaped test piece is formed, and
A Taber abrasion test was performed in accordance with IS K 7311, and the weight reduction was defined as the Taber abrasion reduction. That is, using a H-22 abrasion wheel, applying a load of 9.8 N, abrading 1,000 times at a rotation speed of 60 rpm, measuring the weight loss of the sample before and after the test, and measuring the weight loss of the Taber abrasion loss. did.

(Reference Example 1: Production of thermoplastic polyurethane used in Examples and Comparative Examples)
Polyester diol (PMPA) obtained by condensation polymerization of methyl-1,5-pentanediol and adipic acid
(Number average molecular weight 1500) as 1,4-
A thermoplastic polyurethane was produced using butanediol (BD) and 4,4′-diphenylmethane diisocyanate (MDI), which was heated and melted at 50 ° C. as an organic diisocyanate.

The molar ratio of PMPA: BD: MDI is 1:
The two components are continuously and coaxially rotated using their respective metering pumps so that 2.6: 3.6 and the total supply of these three components is 300 g / min. Machine (30mmφ, L / D = 36, cylinder temperature:
(75-260 ° C.) to carry out continuous melt polymerization to produce a thermoplastic polyurethane. The resulting thermoplastic polyurethane melt was continuously extruded into water in the form of a strand, then cut into pellets with a pelletizer, and the pellets were dehumidified and dried at 80 ° C. for 20 hours to obtain a thermoplastic polyurethane. . The logarithmic viscosity of the obtained thermoplastic polyurethane was 1.01, and the hardness was 90.

(Reference Example 2: Production of thermoplastic polyurethane used in Examples and Comparative Examples)
Polyester diol (PMPA) obtained by condensation polymerization of methyl-1,5-pentanediol and adipic acid
(Number average molecular weight of 3500) as 1,4-
A thermoplastic polyurethane was prepared by using butanediol (BD) and 4,4′-diphenylmethane diisocyanate (MDI) which were heated and melted at 50 ° C. as an organic diisocyanate.

The molar ratio of PMPA: BD: MDI is 1:
The three components are continuously and coaxially rotated in a twin-screw extruder using their respective metering pumps so that 2.4: 3.4 and the total supply amount of these three components is 300 g / min. Machine (30mmφ, L / D = 36, cylinder temperature:
(75-260 ° C.) to carry out continuous melt polymerization to produce a thermoplastic polyurethane. The resulting thermoplastic polyurethane melt was continuously extruded into water in the form of a strand, then cut into pellets with a pelletizer, and the pellets were dehumidified and dried at 80 ° C. for 20 hours to obtain a thermoplastic polyurethane. . The logarithmic viscosity of the obtained thermoplastic polyurethane was 1.05, and the hardness was 70.

(Reference Example 3: Preparation of thermoplastic polyurethane used in comparative example)
Polyester diol (PMPA) (number average molecular weight 1500) obtained by condensation polymerization of 1,5-pentanediol and adipic acid, 1,4-butanediol (BD) as a chain extender, and 50 ° C. as an organic diisocyanate
A thermoplastic polyurethane was produced using each of 4,4′-diphenylmethane diisocyanate (MDI) heated and melted in the above.

The molar ratio of PMPA: BD: MDI is 1:
2.7: 3.6 and the three components are continuously and coaxially rotated by twin-screw extrusion using respective metering pumps so that the total supply amount of these three components is 300 g / min. Machine (30mmφ, L / D = 36, cylinder temperature:
(75-260 ° C.) to carry out continuous melt polymerization to produce a thermoplastic polyurethane. The resulting thermoplastic polyurethane melt was continuously extruded into water in the form of a strand, then cut into pellets with a pelletizer, and the pellets were dehumidified and dried at 80 ° C. for 20 hours to obtain a thermoplastic polyurethane. . The logarithmic viscosity of the obtained thermoplastic polyurethane was 0.55, and the hardness was 90.

(Reference Example 4: Preparation of thermoplastic polyurethane used in Examples and Comparative Examples)
Polyester diol (PMP) obtained by condensation polymerization of -methyl-1,5-pentanediol and adipic acid
A) (number average molecular weight 1500) was converted to 1,
A thermoplastic polyurethane was produced using 4-butanediol (BD) and 4,4′-diphenylmethane diisocyanate (MDI), which was heated and melted at 50 ° C. as an organic diisocyanate.

The molar ratio of PMPA: BD: MDI is 1:
The three components are continuously and coaxially rotated using their respective metering pumps so that 2.6: 3.56 and the total supply of these three components is 300 g / min.
The mixture was supplied to a screw extruder (30 mmφ, L / D = 36, cylinder temperature: 75 to 260 ° C.) to perform continuous melt polymerization to produce a thermoplastic polyurethane. After continuously extruding the resulting thermoplastic polyurethane melt into water in the form of strands, chopped into pellets with a pelletizer,
The pellets were dehumidified and dried at 80 ° C. for 20 hours to obtain a thermoplastic polyurethane. The logarithmic viscosity of the obtained thermoplastic polyurethane was 0.8 and the hardness was 90.

(Reference Example 5: Preparation of thermoplastic polyurethane used in Examples)
Polyester diol (PMPA) (number average molecular weight 1500) obtained by condensation polymerization of 1,5-pentanediol and adipic acid, 1,4-butanediol (BD) as a chain extender, and 50 ° C. as an organic diisocyanate
A thermoplastic polyurethane was produced using each of 4,4′-diphenylmethane diisocyanate (MDI) heated and melted in the above.

The molar ratio of PMPA: BD: MDI is 1:
The three components are continuously and coaxially rotated using their respective metering pumps so that 2.6: 3.75 and the total supply of these three components is 300 g / min.
The mixture was supplied to a screw extruder (30 mmφ, L / D = 36, cylinder temperature: 75 to 260 ° C.) to perform continuous melt polymerization to produce a thermoplastic polyurethane. After continuously extruding the resulting thermoplastic polyurethane melt into water in the form of strands, chopped into pellets with a pelletizer,
The pellets were dehumidified and dried at 80 ° C. for 20 hours to obtain a thermoplastic polyurethane. The logarithmic viscosity of the obtained thermoplastic polyurethane was 1.5 and the hardness was 90.

Examples 1 to 6 and Comparative Examples 1 to 6 The thermoplastic polyurethanes obtained in Reference Examples 1 to 5 and (meth)
The acrylic acid alkyl ester copolymer (A) or (B) and the foaming agent were combined and uniformly mixed as shown in Table 2 to obtain a foamable polyurethane composition for injection molding. This was charged into an injection molding machine (model: FS80S12ASE, manufactured by Nissei Plastic Industry Co., Ltd.), and the length was 60 mm.
Injection molding was performed in a strip-shaped mold having a width of 30 mm and a thickness of 5 mm under the conditions shown in Table 1 to obtain a foam molded product.

[0069]

[Table 1]

The above-mentioned foam molded article was evaluated as described above, and the results are shown in Table 2.

[0071]

[Table 2]

In Table 2, (A) is a (meth) acrylic acid alkyl ester-based copolymer having a number average molecular weight of 3.1 million [Mitaprene P530A, Mitsubishi Rayon Co.], and (B) is a number average molecular weight of 27. Man-made (meth) acrylic acid alkyl ester copolymer [Mitsubishi Rayon Co., Ltd. “metaprene P570A”]. The blowing agent is an azodicarbonamide-based blowing agent (“Vinihome AC” manufactured by Eiwa Chemical Co., Ltd.).
# 3 ").

As is apparent from the results in Table 2, for a thermoplastic polyurethane having a logarithmic viscosity within a specific range,
In the case of each example in which a (meth) acrylic acid alkyl ester-based copolymer having a molecular weight within a specific range was blended in an appropriate amount, an injection-foamed molded article of a thermoplastic polyurethane of a desired quality was obtained, In Comparative Examples 2 and 3 using an alkyl (meth) acrylate copolymer having a molecular weight outside the specified range, the shapes and dispersion of bubbles were not uniform and the appearance was inferior.

Although the same (meth) acrylic acid alkyl ester copolymer as in the examples was used, Comparative Examples 4 and 5, which used a small amount of the copolymers, were not preferable in terms of bubble dispersion state and appearance. Further, in the case of Comparative Example 6 in which the same (meth) acrylic acid alkyl ester-based copolymer as in the example was used in a large amount exceeding a specific range, the specific gravity, the bubble dispersion state, and the abrasion loss were inferior. . Further, in the case of Comparative Example 1 in which the same (meth) acrylic acid alkyl ester-based copolymer as in the example was used, but the thermoplastic polyurethane having a logarithmic viscosity out of the specified range was used, the bubble dispersion state, the appearance shape, and the The abrasion was poor.

[0075]

According to the present invention, a thermoplastic polyurethane having a specific range of logarithmic viscosity, an alkyl (meth) acrylate polymer having a specific range of number average molecular weight, and an organic pyrolytic foaming agent having a specific range of decomposition temperature. Injection-foamed thermoplastic polyurethane molded by injection foaming is excellent in abrasion resistance, scratch resistance, shock absorption, etc., and has a low specific gravity, so it can be used as a lightweight molded product, cushioning material, cushion, etc. Specifically, the material is useful for cushioning materials and parts of portable equipment such as shoe soles, various grips, stereos with headphones, computers, and handy terminals.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 75/04 C08L 75/04 // (C08L 75/04 33:06) B29K 75:00 105: 04 F term (reference) ) 4F050 AA01 AA06 BA01 HA56 HA59 HA73 KA11 NA52 4F074 AA48A AA78A BA13 BA16 BA18 CA26 CC22X DA09 DA19 DA33 DA45 4F206 AA21E AA31 AE10 AG20 AH26 AH42 AM32 JA04 JF01 JF04 JQ81 4J05 BG04 CK04 BG04 CK04

Claims (6)

[Claims] 1. A resin having a number average molecular weight of 1 to 100 parts by weight of a thermoplastic polyurethane having a logarithmic viscosity of 0.7 to 2.0 dl / g.
An injection foamed molded product comprising a thermoplastic polyurethane composition containing 500,000 to 6,000,000 alkyl (meth) acrylate-based polymers in an amount of 2 to 20 parts by weight. 2. The molded article according to claim 1, wherein the Taber abrasion loss is 70 mg or less. 3. The molded article according to claim 1, wherein a skin layer is molded on the surface. 4. A portable device housing having the molded product according to claim 1 on the outermost surface. 5. A shoe sole comprising the molded product according to claim 1. 6. An alkyl ester (meth) acrylate having a number average molecular weight of 1.5 to 6,000,000 per 100 parts by weight of a thermoplastic polyurethane having a logarithmic viscosity of 0.7 to 2.0 dl / g. 20 parts by weight and decomposition temperature of 1
A method for producing an injection-foam molded article comprising a thermoplastic polyurethane composition, which comprises blending 0.5 to 10 parts by weight of an organic thermal decomposition type foaming agent at 20 to 220 ° C and injection foaming.