JPH05179050A - Polyolefin-based resin foam particle - Google Patents

Abstract

PURPOSE:To provide the subject resin foam particles composed of a specified alpha-olefin-propylene copolymer and a specified ethylene-based copolymer, having a prescribed shear-sensitivity and a uniform and relatively large cell diameter, excellent in visual appearance, heat resistance and compression strength and useful as a foamed-in-place material, etc. CONSTITUTION:The objective resin foam particles are produced from a resin composition as the base resin, composed of (A) 100 pts.wt. alpha-olefin-propylene copolymer containing, as its constituting component, a 4 to 8C alpha-olefin such as butene-1 and (B) preferably 5 to 100 pts.wt. ethylene-based copolymer containing, as the constituting component, an unsaturated ester such as vinyl acetate or an unsaturated ether such as vinyl methyl ether and having 0.3 to 0.70 shear-sensitivity of viscosity measured at 200 deg.C.

Description

Detailed Description of the Invention

[0001]

The present invention has a uniform bubble diameter,
The present invention relates to a polyolefin resin foamed particle capable of producing an in-mold foam molded article having excellent surface appearance and physical properties, and the foamed particle of the present invention is a packaging container, toy, core material for automobile bumper, helmet core material, packaging. It is useful for the production of in-mold foam moldings used as cushioning materials and the like.

[0002]

2. Description of the Related Art In-mold foam moldings of polyolefin resin foam particles such as polypropylene and high-density polyethylene are superior to polystyrene foam moldings in heat resistance, chemical resistance, impact resistance, compression elastic recovery rate, etc. Therefore, it is used as a core material for bumpers, packaging containers, carrying boxes for machine parts, etc.

However, in the conventional polyolefin resin foamed particles, since the cell diameter is not sufficiently uniform,
The foamed molded product obtained is inferior in physical properties such as surface appearance and compressive strength. As a method for improving the nonuniformity of the bubble diameter of the foamed particles, conventionally, a low density ethylene / propylene copolymer has been used. A method in which a mixture of polyethylene and / or ethylene / vinyl acetate copolymer is used as a base resin (Japanese Patent Publication No. 59-23731), and a method in which a carboxyl group-containing polymer is mixed with a polyolefin resin (Japanese Patent Application Laid-Open No. Sho-59-37) No. 62-115042) has been proposed.

[0004]

The conventional method for improving the nonuniformity of the cell diameter of the polyolefin resin expanded particles is as follows.
In the former method, as the mixing ratio of low-density polyethylene or ethylene-vinyl acetate copolymer increases, the effect of uniform cell size disappears, which in turn lowers moldability, compressive strength as a foamed molded product, heat resistance, etc. There is a problem that the physical properties are deteriorated, and the latter method has a problem that the surface appearance of the molded product is poor due to a poor mold release during the production of the foamed molded product.

An object of the present invention is to provide a foamed particle capable of producing a polypropylene resin in-mold foamed molded article having a uniform foamed cell diameter and excellent moldability and physical properties. This in-mold foamed product has a uniform cell diameter and excellent moldability, so that the appearance of the molded product is beautiful, and since it has excellent physical properties, it can be used in a wide range of applications.

[0006]

Means for Solving the Problems As a result of investigations for solving the above problems, the present inventors have found that an α-olefin / propylene copolymer (A) containing an α-olefin having 4 to 8 carbon atoms is used. , An ethylene-based copolymer (B) containing an unsaturated ester or an unsaturated ether as a copolymerization monomer, and a shear sensitivity (N) of viscosity measured at 200 ° C. is 0.30.
The in-mold foamed molded product molded with polyolefin resin foamed particles using a resin composition having a resin composition of up to 0.70 as a base resin has a uniform cell diameter and excellent moldability, so the molded product has a beautiful appearance and is further compressed. They found that they have excellent physical properties such as strength and heat resistance, and completed the invention.

In the present invention, as the α-olefin as a raw material of the α-olefin / propylene copolymer (A) which is the first component, butene-1, pentene-1, octene-
Monomers having 4 to 8 carbon atoms such as 1,4-methylpentene-1 are used, and those obtained by copolymerizing one or more of these with propylene are used. The α-olefin content is preferably 3 to 17% by weight. As the α-olefin / propylene copolymer of the present invention, especially butene-1 is 3
A butene-1 / propylene copolymer containing about 12 to 12% by weight is preferable.

Among the ethylenic copolymers (B) containing the unsaturated ester or unsaturated ether as the second component in the present invention, the unsaturated ester is
Vinyl esters such as vinyl acetate, vinyl butyrate, vinyl pivalate, and vinyl carbonate; acrylate-based esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, and 2-ethylhexyl acrylate; and methyl methacrylate, n. One or more of methacrylate-based esters such as -butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate and 2-ethylhexyl methacrylate, and fumarate-based esters such as diethyl fumarate and di-n-butyl fumarate are used. .. As the unsaturated ether, one or more kinds of vinyl methyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl β-hydroxy ether and the like are used. In the present invention, as the component (B), an ethylene-vinyl acetate copolymer containing 3 to 30% by weight of a vinyl acetate component and an ethyl acrylate component of 3 are particularly preferable.
~ 30 wt% ethylene-ethyl acrylate copolymer is preferred.

In the present invention, the resin composition comprising the resin of the first component (A) and the resin of the second component (B) is used as the base resin. In this case, the resin (A) mainly imparts physical properties such as mechanical strength and heat resistance of the in-mold foam molded article, while the resin (B) mainly homogenizes the bubble diameter of the foamed particles. , Plays a role of improving the moldability and surface appearance of the molded product foamed in the mold. Therefore, in setting the composition ratio in the present invention, it is necessary to select the resins of (A) and (B) and to make a decision by sufficiently considering the expected effect. In the present invention, the composition ratio is not limited, but generally, with respect to 100 parts by weight of the resin (A),
The resin (B) is 5 to 100 parts by weight. As described above, the resin (B) is mainly intended to make the bubble diameters of the foamed particles uniform, and even if the ratio is too high, the intended effect is not remarkable, and conversely (A) The excellent properties such as the physical properties and heat resistance of the resin) are not exhibited.

In the present invention, for example, an antioxidant, an ultraviolet absorber, a lubricant, an antistatic agent, a flame retardant, a filler, a nucleating agent and the like are mixed with the resin composition (base resin), if necessary. You can The amount to be mixed is decided in consideration of economical efficiency and required quality, but generally 5% by weight based on the base resin.
It is preferably 2% by weight or less. In the present invention, the composition is prepared by solution mixing, melt mixing and melt kneading, but melt kneading is generally used. For example, various kneaders such as rolls, screws, Banbury mixers, kneaders, blenders, and mills are used to knead the mixture at a desired temperature, and after kneading, the granules are granulated to an appropriate size. In this case, any method such as a strand cutting method, an underwater cutting method, a hot cutting method, a mist cutting method, a sheet cutting method, a freeze pulverization method, and a melt spraying method may be used.

The shear sensitivity of the viscosity of the base resin in the present invention can be measured by a capillary rheometer or the like. In the present invention, the Shimadzu Flow Tester CFT- manufactured by Shimadzu Corporation is used.
Using 500C, set the die heater temperature to 200 ℃,
Using a die with a diameter of 1 mm and a length of 10 mm, the shear rate and shear stress were measured by changing the load applied to the piston, the relationship between the two was plotted in a log-log graph, and the quadratic correlation was determined by the least squares method. Create a correlation graph for both. From this graph, the shear rate is 10 (1 / sec) and 1
The shear stress at 000 (1 / sec) was read, and the shear sensitivity was calculated according to the following formula.

[0012]

[Equation 1]

However, S₁= Shear rate 10 (1 / sec)
Shear stress against (dyn / cm ²), S₂= Shear
Shear stress (dyn /
cm ₂) In the present invention, the shear sensitivity of the viscosity of the base resin
A composition of 0.30 to 0.70 is selected. Especially preferred
It is preferably 0.35 to 0.60. This feeling of shear
The degree of α-olefin propylene that constitutes the base resin composition is
Ren copolymer (A) and unsaturated ester or unsaturated ether
Of an ethylene-based copolymer (B) containing ethylene as a copolymerization monomer
Resin molecular weight, molecular weight distribution and copolymer composition
Or, affected by the dispersed state of the composition, the base resin composition
Reflect the matrix. In the present invention, the viscosity of the base resin
If the shear sensitivity of the degree is 0.70 or more, the sea of the resin composition
The molecular weight distribution of the resin constituting the resin is narrow or dispersed
It means that the foamed particles made of these base resins are used.
The temperature range for producing foams has become narrower
Therefore, the closed cell ratio of the obtained foam is reduced, which is preferable.
I don't. On the other hand, the shear sensitivity of the viscosity of the base resin is less than 0.3
In the case of, the molecular weight distribution of the resin composition is too wide,
By mixing (A) and (B), a certain gel state
It is estimated that this is due to the fact that the
If the foam ratio cannot be obtained or the expanded particles are molded in the mold,
In this case, the fusion of the foamed particles to each other becomes worse.

In the present invention, the expanded particles are produced by the Dokan method (Patent Office, March 63, illustrated IPC) or the extrusion foaming method (Japanese Patent Laid-Open No. 58-76230). For example, in the case of the docan method, the base resin particles are dispersed in water in a closed container, then a volatile expanding agent is supplied in the closed container, and after heating the dispersion liquid to a temperature equal to or higher than the softening point of the resin particles, Manufactured by opening the discharge port provided below the water surface in a closed container and discharging an aqueous dispersion containing resin particles impregnated with a swelling agent into an atmosphere (atmosphere) at a pressure lower than the pressure in the closed container. To be done. At the time of this production, it is preferable to pressurize the inside of the container with air or nitrogen gas to facilitate the discharge.

In the present invention, as the volatile expansion agent, for example, aliphatic hydrocarbons such as butane, pentane, hexane, heptane; trichlorofluoromethane, dichlorofluoromethane, tetrachlorodifluoroethane, dichlorotetrafluoromethane, methylene chloride. , Halogenated hydrocarbons such as ethyl chloride, etc. may be used alone or in combination of two or more. Also, inorganic gases such as nitrogen, air and carbon dioxide can be used.

The amount of the volatile expanding agent added varies depending on the kind of the expanding agent and the intended bulk density of the resin particles, but is usually 10 to 80 parts by weight with respect to 100 parts by weight of the resin particles. As a dispersant for dispersing resin particles in water, aluminum oxide, titanium oxide, calcium carbonate,
Inorganic suspending agents such as basic magnesium carbonate and tricalcium phosphate; water-soluble polymeric protective colloid agents such as polyvinyl alcohol, methylcarboxycellulose, N-polyvinylpyrrolidone; sodium dodecylbenzenesulfonate, sodium alkanesulfonate, alkyl Sodium sulfate ester, sodium olefin sulfate ester,
Examples thereof include anionic surfactants such as acylmethyl taurine and sodium dialkylsulfosuccinate. Among these, it is preferable to use tribasic calcium phosphate having a particle size of 0.01 to 0.8 micron in combination with a suspension aid of sodium dodecylbenzenesulfonate. This fine tribasic calcium phosphate contains phosphoric acid in an amount of 0.60 to .0 per 1 mol of calcium hydroxide. It is obtained by reacting in water at a ratio of 067 mol.

The amount of water as a dispersion medium is 100 to 1,000 parts by weight, preferably 200 to 1,000 parts by weight, based on 100 parts by weight of the resin particles.
It is 500 parts by weight. If the amount is less than 150 parts by weight, the resin particles are likely to block each other during heating and pressurization. 1,000
If the amount is more than parts by weight, the productivity of the expanded beads decreases, which is not economical. An aqueous dispersion of polyolefin-based resin particles dispersed in water by a dispersant is supplied with a gaseous expander or a liquid expander in a closed container and heated to a temperature equal to or higher than the softening point of the resin. By heating, the pressure in the container rises and the expander is impregnated in the resin particles. Next, the resin particles are discharged into a low pressure region (generally at atmospheric pressure) from the closed container together with water through a discharge port such as a slit or a nozzle provided in the lower part of the closed container, to obtain polyolefin resin foamed particles.

In the production of the expanded beads, it is preferable to supply an inorganic gas such as nitrogen, helium or air to the closed container before or after adding the expanding agent into the closed container to apply pressure. The inorganic gas may be supplied before or after heating the dispersion liquid. The supply of air, nitrogen gas, or an inorganic gas such as argon into the closed container facilitates the impregnation of the expander with the resin particles, and serves to obtain the polyolefin resin expanded particles having a low bulk density.

The foamed particles released into the atmosphere are dried (cured) in a room at 30 to 65 ° C. to remove water adhering to the surface, and used for molding a cushioning material, a container and the like. Various conventionally known methods can be used as the molding method. After filling the polyolefin resin foamed particles into the mold, compress the volume of the foamed particles to reduce by 15 to 50%,
Then, a compression molding method (DOS2107683) in which 1 to 5 kg / cm ² G of steam is introduced to fuse the expanded particles to each other and then the mold is cooled to obtain a product. A method for obtaining a product by preliminarily impregnating expanded particles with a volatile liquid expansion agent to give secondary expanded ability to the expanded particles, then filling the mold, heating with steam to perform secondary expansion, and fusing particles together .. The expanded particles were put in a closed chamber, and then an inorganic gas such as air or nitrogen gas was injected into the chamber to increase the pressure in the cells of the expanded particles to give a secondary foaming ability, and this secondary foaming ability was given. Fill the mold with particles and heat with steam, 2
Subsequent foaming and fusion of particles to obtain a product (so-called pressure aging method; JP-B-59-23731)
issue). The foamed particles were placed in a mold whose pressure was increased to 1.0 to 6.0 kg / cm ² G with a pressurized gas and the pressure of the mold was 0.5 kg / c.
While compressing using a pressurized gas having a m ² or higher, the mold is divided into a plurality of times and sequentially filled, and the mold pressure is kept at the mold pressure during the filling, and then the mold pressure after the completion of the filling. To atmospheric pressure and then heating with steam to fuse the expanded particles together, and at that time,

[0020]

[Equation 2]

[In the formula, W, V and ρ represent the following, respectively. W ... Weight of molded product (g) V ... Volume of molded product (liter) ρ ... Bulk density of foamed particles in air (g / liter)] Method for controlling the compression ratio to 40 to 70% ( JP-A-62-151325). A pressurizing gas having a pressure of 0.5 to 5.0 kg / cm ² G and a pressurizing gas higher than the internal pressure of the mold of 0.5 kg / cm ² or more was used for 1 hour or more in advance. The obtained expanded particles to which the gas internal pressure is applied are divided into a plurality of times using a pressurized gas having a pressure of 0.5 kg / cm ² or more higher than the above-mentioned pressure in the mold and sequentially filled, and the inside of the mold is filled during the filling. The pressure is continuously maintained at the mold pressure, and after completion of the filling, the mold pressure is returned to atmospheric pressure, and then heating with steam is performed to fuse the expanded particles, and the expanded particles are represented by the same formula as above. A method of controlling the compression rate to less than 40% (excluding 0%). The foamed particles themselves are filled with foamed particles having a secondary foaming ability in a mold cavity under normal pressure or filled in a mold under pressure and heated by steam to secondary-foam and fuse the particles together. Method for obtaining a product (Japanese Patent Laid-Open No. 62-128)
No. 709, No. 63-256634, No. 63-2589.
39, 63-107516).

Any of the above-mentioned molding methods may be used, and the molding method is selected in consideration of the properties of the expanded particles, the shape of the molded body, the density and the like. Hereinafter, the present invention will be described in more detail with reference to Examples.
The parts and% in the examples are based on weight.

[0023]

【Example】

[Example 1] Butene-1 content 8.5%, MFR 8g / 1
80% by weight of butene-1 / propylene random copolymer for 0 minutes, 8% of vinyl acetate content, 20% by weight of ethylene / vinyl acetate copolymer for MFR of 4 g / 10 minutes, caliber 65 mm
After kneading at 220 ° C. with a single-screw extruder to prepare a composition,
It was cut in water through a die orifice having a diameter of 0.8 mm to prepare base resin particles having a size of about 1.3 mg / grain. The shear sensitivity of the viscosity of this base resin at 200 ° C. is 0.
It was 45.

Subsequently, 250 parts of water, 100 parts of the above-mentioned base resin particles, 1.0 part of tricalcium phosphate having a particle size of 0.3 to 0.5 micron, and 0.007 part of sodium dodecylbenzenesulfonate are placed in a closed container. (Filling rate 62%), and then nitrogen gas under stirring with the internal pressure of the sealed container being 5 kg / cm.
^The pressure was increased to ² G, and the supply of nitrogen gas was stopped. Then, 25 parts of butane was fed into the closed container, heated to 136 ° C. over 1 hour, and kept at the same temperature for 45 minutes. The autoclave internal pressure was 23 kg / cm ² G.

After that, the valve of the discharge nozzle at the bottom of the closed container was opened, and the dispersion liquid was discharged into the atmospheric pressure in about 2 seconds for foaming. The internal pressure of the closed container at the moment when the final portion of the dispersion liquid was discharged from the closed container was about 10 kg / cm ² G. Also, during the discharge of the dispersion liquid, the temperature of the closed container was adjusted to 136
It was maintained at ° C. The foamed particles thus obtained had a bulk density of 22 g / liter, a particle size of 4.0 mm, and a foamed cell diameter of 220 μm, and had a uniform cell shape. Further, blocking of the foamed particles was not observed.

The foamed particles were left to stand at room temperature for 2 days to be dried, and then aged under pressure with 2 kg / cm ² G of pressurized air in a 2 m ³ pressure vessel for 24 hours. It was 0.5 kg / cm ² G. Then, the foamed particles were filled in a mold having steam holes, and 2.8 kg / cm ²
The steam of G was introduced, the expanded particles were heat-fused to each other, then, cooled with water for 120 seconds and allowed to cool for 35 seconds, and then the molded product was taken out from the mold.

The molded product has a density of 23 g / liter and a length of 60.
It was 0 mm, 900 mm in width, and 50 mm in thickness, and it was a molded product excellent in surface appearance with few surface gaps and no irregularities. Further, when it was broken from the center of the molded product, 90% of the cross-section of the molded product was an excellent molded product in which the expanded particles were fused.

From this molded product, length 50 mm, width 50 m
m, thickness of 25 mm sample for compression test, length 150 m
Samples for heat resistance test of m, 150 mm in width, and 50 mm in thickness were obtained by cutting 5 points respectively. Compression test is NDS-Z
According to 0504, compress at a compression speed of 10 mm / min, and
The stress at 0% compression was evaluated as the compressive strength. The heat resistance test is based on JIS-K6767 and the temperature is 120 ° C.
The dimensional change after heating for 22 hours with the hot-air circulation type dryer was evaluated. In the case of this molded body, the compressive strength is 2.2 kg /
In cm ² , the heat-resistant dimensional change was −4%.

[Examples 2 to 6 and Comparative Examples 1 to 5] The results shown in Tables 1 and 2 were obtained in the same manner as in Example 1 except that the composition shown in Table 1 was used as the base resin. It was

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

EFFECTS OF THE INVENTION Since the expanded beads of the present invention have a relatively large and uniform cell size, the appearance of a molded article molded from the particles is beautiful, and the physical properties such as compressive strength and heat resistance are excellent. Therefore, it can be used for a wide range of purposes.

Claims (1)

[Claims] 1. An α-olefin propylene copolymer (A) containing an α-olefin having 4 to 8 carbon atoms and an ethylene copolymer (B) containing an unsaturated ester or an unsaturated ether as a copolymerization monomer. And polyolefin-based resin expanded particles comprising a resin composition having a shear sensitivity of viscosity of 0.30 to 0.70 measured at 200 ° C. as a base resin.