JP3126449B2 - Polyolefin resin foam particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to expanded polyolefin resin particles suitable for producing in-mold foam molded articles useful as packaging containers, toys, automobile bumper core materials, helmet core materials, packaging cushioning materials, and the like. It is.

[0002]

2. Description of the Related Art In-mold bead foam moldings of polyolefin resins such as polypropylene and high-density polyethylene are superior in heat resistance, chemical resistance, impact resistance, and compression elastic recovery to polystyrene foam moldings. It is used for core materials for bumpers, packaging containers, and return boxes for machine parts.

However, polyolefin resin foam molded articles have insufficient cushioning performance. Conventionally, as a technique for improving the cushioning performance, a technique for increasing the rigidity of the base resin of the foam, for example, in the case of a polypropylene foam, A resin having a low ethylene content in the ethylene / propylene random copolymer used as the base resin, or a butene-1 ·
It has been proposed to use a propylene random copolymer (Japanese Patent Laid-Open No. 1-242638).

[0004]

In the case of using a highly rigid base resin which has been conventionally proposed as a means for improving the cushioning performance, the compressive strength of the foam, which is an index of the cushioning performance, certainly increases, and Since the energy absorption amount per unit volume increases, the performance as a buffer material improves. However, since all of the base resins having high rigidity tend to have high crystallinity, there is a problem that, on the contrary, the impact resistance is reduced and the steam pressure at the time of molding must be increased. For example, when an attempt is made to use the butene-1 / propylene random copolymer or propylene homopolymer foam molded article as a cushioning material for packaging, the part protecting the corner of the article to be packaged is broken by impact. However, it has a disadvantage that it does not show sufficient buffering performance. This is considered to be due to the low impact resistance of the foamed molded article and the weak fusion during molding. Therefore, the use of a highly rigid base resin is limited because the design is limited as a cushioning material.

On the other hand, conventionally, as a polyolefin resin foam having excellent impact resistance, an in-mold foam molded article using a low-crystallinity polypropylene copolymer (JP-A-60-110).
Nos. 431 and 60-110934) and in-mold foam molded articles using linear polyethylene (Japanese Patent Publication No. 60-10077, Japanese Patent Application Laid-Open No. 59-187).
Nos. 036 and 64-1741 and 64-29
444). Certainly, these foam moldings are more flexible than high-crystal polypropylene foam moldings,
Although it has excellent impact resistance, it has low compressive strength, and it is necessary to set the density to be large in order to obtain a cushioning property comparable to that of a polypropylene-based foam molded article, which leaves a problem in terms of weight reduction.

In the present invention, foamed particles capable of producing a foamed molded article in a polyolefin resin mold having a low density, excellent shock absorbing performance, high impact resistance, and excellent fusibility even at a low steam pressure. The purpose is to provide. Since the in-mold foam molded article is excellent not only in cushioning performance but also in impact resistance, it can be used for a wide range of applications without being limited by a design aspect in cushioning design.

[0007]

The inventors of the present invention have studied to solve the above problems, and as a result, have found that an α-olefin / propylene copolymer containing an α-olefin having 4 to 8 carbon atoms has a weight of 60 to 95%. % And 1 according to JIS K6300
It is composed of 5 to 40% by weight of a polyolefin rubber having a Mooney viscosity of 10 to 100 measured at 00 ° C.
The flexural rigidity measured according to K7106 is 4,500-
An in-mold foam molded article made of polyolefin-based resin foam particles having a composition of 9,000 kg / cm ² as a base resin has excellent cushioning performance, high impact resistance and low pressure moldability even at a low density. They found that they were excellent and completed the invention.

In the present invention, the α-olefin as the raw material of the α-olefin / propylene copolymer as the first component includes butene-1, pentene-1, octene-1,4-
A monomer having 4 to 8 carbon atoms such as methylpentene-1 is used, and one or more of these monomers are copolymerized with propylene. Its α-olefin content is 3 to
17% by weight is preferred. As the α-olefin / propylene copolymer of the present invention, a butene-1 / propylene copolymer containing 3 to 12% by weight of butene-1 is particularly preferred.

JIS K as the second component in the present invention
Mooney viscosity of 1 measured at 100 ° C according to 6300
Examples of the polyolefin rubber having 0 to 100 include α- such as ethylene, propylene, butene-1, and pentene-1.
A low-crystalline or non-crystalline rubbery copolymer obtained by random copolymerization of two or more types of olefin monomers. The polyolefin rubber may be one obtained by copolymerizing a diene monomer as the third component. In the present invention, among the polyolefin rubbers, JIS K
Those having a Mooney viscosity of 15 to 90 measured at 100 ° C. according to 6700 are preferably used. When the Mooney viscosity is less than 10, the low pressure moldability of the obtained expanded particles is not improved, and when it exceeds 100, the impact resistance of the obtained expanded molded product is not sufficiently improved. The Mooney viscosity of the polyolefin rubber in the present invention is JIS K63.
The measurement was performed using an L-type rotor at a test temperature of 100 ° C., a preheating time of 1 minute, and a rotor operation time of 4 minutes in accordance with Example No. 00.

In the present invention, an α-olefin / propylene copolymer containing an α-olefin having 4 to 8 carbon atoms is contained in an amount of 60 to 95% by weight, preferably 70 to 95% by weight,
A polyolefin rubber having a Mooney viscosity of 10 to 100 is mixed at a ratio of 5 to 40% by weight, preferably 5 to 30% by weight, and a flexural rigidity of 4,500 to 9,000 kg / cm measured according to JIS K7106. The composition of ² is used as a base resin for the expanded particles. In this case, if the flexural rigidity is less than 4,500 kg / cm ² , the impact resistance is high, but the compressive strength is low and the weight cannot be reduced. On the other hand, the flexural rigidity is 9,0
If it exceeds 00 kg / cm ² , the impact resistance is low and not practical.

In the present invention, the flexural rigidity is JIS K
It is measured according to 7106. First, the thickness [h] is about 2 in a state where the base resin is sufficiently melted by a hot press molding machine.
A sheet-shaped molded product having a thickness of mm is produced. Next, this sheet-like molded body was cut into a width [b] of about 15 mm and a length of about 90 mm, the distance between supports [S] was 3 cm, the moment of the pendulum [M ₀ ] was 6 kg · cm, and the bending angle scale was set. [Φ]
Read the load scale [n] at 0.1745 radians,
It is calculated by the following equation.

[0012]

(Equation 1)

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 may be mixed with the composition (base resin) as required. it can. The mixing amount is determined in consideration of economy and required quality, but is generally 5% by weight or less, preferably 2% by weight or less based on the base resin. In the present invention, solid mixing by kneading is generally used to produce the composition. For example, kneading using a screw type extruder, Banbury mixer, mixing roll, etc.
After kneading, the mixture is granulated to a suitable size. In this case, any method such as a strand cutting method, an underwater cutting method, a sheet cutting method, a freeze pulverizing method, and a melting spraying method may be used.

In the present invention, the foamed particles are produced by the docan method (IPC illustrated in March 63, JP Office) or the extrusion foaming method (JP-A-58-76230). For example, in the case of the docan method, the base resin particles are dispersed in water in a closed container, and then a volatile expanding agent is supplied into the closed container, and after heating the dispersion to a temperature equal to or higher than the softening point of the resin particles, Manufactured by opening a 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. Is done. In this production, it is preferable to pressurize the inside of the container with air or nitrogen gas to facilitate discharge.

In the present invention, examples of the volatile swelling agent include aliphatic hydrocarbons such as butane, pentane, hexane and heptane; trichlorofluoromethane, dichlorofluoromethane, tetrachlorodifluoroethane, dichlorotetrafluoromethane and methylene chloride. And halogenated hydrocarbons such as ethyl chloride can be used alone or in combination of two or more. Also, air, nitrogen gas,
Inorganic gases such as carbon dioxide can be used. The amount of the volatile expanding agent varies depending on the type of the expanding agent and the bulk density of the target resin particles.
It is 10 to 80 parts by weight with respect to 00 parts by weight.

As dispersants for dispersing the resin particles in water, aluminum oxide, titanium oxide, calcium carbonate,
Inorganic suspending agents such as basic magnesium carbonate and tribasic calcium phosphate; water-soluble polymeric protective colloid agents such as polyvinyl alcohol, methylcarboxycellulose, N-polyvinylpyrrolidone; sodium dodecylbenzenesulfonate, sodium alkanesulfonate, alkyl Sodium sulfate, sodium olefin sulfate,
And anionic surfactants such as acylmethyltaurine and sodium dialkylsulfosuccinate. Among these, it is preferable to use tribasic calcium phosphate having a particle size of 0.01 to 0.8 μm in combination with sodium dodecylbenzenesulfonate as a suspending aid. The fine tribasic calcium phosphate is obtained by reacting phosphoric acid in water at a ratio of 0.60 to 0.67 mol with respect to 1 mol of calcium hydroxide.

The amount of water as a dispersion medium per 100 parts by weight of the resin particles is 150 to 1,000 parts by weight, preferably 2 to 1000 parts by weight.
It is 00 to 500 parts by weight. If the amount is less than 150 parts by weight, the resin particles are likely to be blocked when heated and pressed.
If the amount exceeds 1,000 parts by weight, the productivity of the foamed particles is reduced, which is not economical. A gaseous expanding agent or a liquid expanding agent is supplied in an airtight container to an aqueous dispersion of polyolefin-based resin particles dispersed in water by a dispersant, and heated to a temperature equal to or higher than the softening point of the resin. The pressure in the container is increased by heating, and the expanding agent is impregnated into the resin particles. Subsequently, the polyolefin-based resin foam particles are obtained by discharging the resin particles together with water from a discharge port such as a slit or a nozzle provided in a lower portion of the closed container into a low-pressure region (generally at atmospheric pressure) from the closed container.

The foamed particles released into the atmosphere are dried (cured) in a room at 30 to 65 ° C. in order to remove water adhering to the surface, and are used for forming a cushioning material, a container and the like. As a molding method, various conventionally known methods can be used. After filling the polyolefin-based resin expanded particles into the mold, compress the expanded particles to reduce the volume by 15 to 50%,
Then, a steam of 1 to 5 kg / cm ² G is introduced to fuse the foamed particles together, and then the mold is cooled to obtain a product by a compression molding method (DOS2107683). A method of obtaining a product by impregnating a foamed particle with a volatile liquid expanding agent in advance and imparting a secondary foaming ability to the foamed particle, filling the mold, heating with steam, secondary foaming and fusing the particles together. . The foamed particles are placed in a closed chamber, and then the pressure inside the cells of the foamed particles is increased by pressurizing an inorganic gas such as air or nitrogen gas into the chamber to impart a secondary foaming ability, and the secondary foaming ability is imparted. Fill the mold with particles, heat with steam,
A method of obtaining a product by foaming and fusing particles together (so-called pressure aging method; Japanese Patent Publication No. 59-23731)
issue). In a mold pressurized to 1.0 to 6.0 kg / cm ² G with a pressurized gas, the foamed particles are placed at a pressure of 0.5 kg / c from the pressure in the mold.
while compressing with m ² or more high pressure gas, and then filled sequentially in a plurality of times, continuing to hold the mold internal pressure during its filling into a mold internal pressure of the then-mold pressure after completion of filling Is returned to the atmospheric pressure, and then heated by steam to fuse the foamed particles together.

[0019]

(Equation 2)

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

Any of the above molding methods may be used, and the selection is made in consideration of the properties of the foamed particles, the shape and density of the molded product, and the like. Hereinafter, the present invention will be described in more detail with reference to examples.
In the examples, parts and% are based on weight.

[0022]

【Example】

Example 1 Butene-1 having a butene-1 content of 7.5% by weight
80% by weight of propylene random copolymer and 20% by weight of ethylene / propylene copolymer rubber having Mooney viscosity of 85
Was kneaded at 225 ° C. with a single-screw extruder having a diameter of 65 mm to form a composition, extruded into a strand having a diameter of 1 mm, cooled in a water bath, and then cut at a size of about 1.8 mg / particle to obtain a base resin. Particles were created. The bending rigidity of the base resin was 6,900 kg / cm ² .

Subsequently, 250 parts of water, 100 parts of the above-mentioned base resin particles, 1.0 part of tribasic calcium phosphate having a particle size of 0.3 to 0.5 micron and 0.007 parts of sodium dodecylbenzenesulfonate are placed in a closed container. (Filling rate: 62%), and then, while stirring, nitrogen gas is introduced into the closed vessel to reduce the internal pressure to 5 kg / cm.
^The pressure was increased to ² G, and the supply of nitrogen gas was stopped. Then, 25 parts of butane was supplied into the closed container, heated to 138 ° C. over 1 hour, and kept at the same temperature for 15 minutes. As a result, the internal pressure of the autoclave showed 23 kg / cm ² G.

Thereafter, the valve of the discharge nozzle at the bottom of the closed vessel was opened, and the dispersion was released into the atmosphere at about 2 seconds to effect foaming. The internal pressure of the sealed container was about 10 kg / cm ² G at the moment when the final portion of the dispersion was discharged from the closed container. During the dispersion discharge, the temperature of the closed
Maintained at 8 ° C. The expanded particles thus obtained are
The bulk density was 22 g / cm ³ , the particle size was 4.5 mm, and the foam cell diameter was 200 microns. In addition, no blocking between the expanded particles was observed.

The foamed particles were left in a room at 40 ° C. for 2 days and dried, and then 2 kg / cm ² G in a 2 m ³ pressure vessel.
When pressure aging was performed with pressurized air for 24 hours, the internal pressure of the foamed particles was 0.3 kg / cm ² G. The particles are then filled into a mold having steam holes,
Guide ² G steam, heat and fuse the foamed particles together,
Next, after water cooling for 120 seconds and cooling for 20 seconds, the molded product was taken out from the mold. The molded product has a density of 24 g / liter and a length of 6
It had a thickness of 00 mm, a width of 900 mm, and a thickness of 50 mm. Also, when the molded article was broken from the center, it was an excellent molded article in which expanded particles of about 95% of its cross section were fused.

From this molded product, 50 mm long and 50 m wide
m, 25mm thick compression test sample, 40m long
Samples for an impact test having a length of 200 mm, a width of 200 mm, and a thickness of 20 mm were obtained by cutting 5 points and 20 points, respectively. The compression test conforms to NDS-Z0504 and has a compression speed of 10 mm.
/ Min, and the stress at 50% compression was evaluated as the compressive strength. In addition, the impact resistance test was conducted according to JIS K7211.
To drop the steel ball 255g according to evaluated the 50% breaking height H ₅₀ in accordance with the following equation.

[0027]

(Equation 3)

H ₅₀ : 50% breaking height (cm) H ₁ : Test height (cm) when height level (i) is 0 d: Height interval (cm) when raising and lowering test height i: when of an H ₁ and 0, the height level n _i one by one increases or decreases: (not or destroyed) was disrupted at each level
Number of test pieces N: total number of broken (or not broken) test pieces (N = Σn _i ) ± 1/2: negative sign was used when the broken data was used, and data that was not broken was used Sometimes it takes the plus sign.

In the case of this molded product, the compressive strength is 2.3 kg.
/ Cm ² , the 50% breaking height was 80 cm.

Examples 2 to 6, Comparative Examples 1 to 4 The results shown in Tables 1 and 2 were obtained in the same manner as in Example 1 except that the resins shown in Table 1 were used as the resin particles.

[0031]

The foamed particles of the present invention have excellent fusibility even at a low steam pressure, and a molded article formed by using the foamed particles has a low density, a high compressive strength, and an excellent impact resistance. It can be used at

[0032]

[Table 1]

[0033]

[Table 2]

──────────────────────────────────────────────────続 き Continued on front page Examiner Yasue Uchida (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 9/18

Claims (1)

(57) [Claims] 1. A polyolefin having 60 to 95% by weight of an α-olefin / propylene copolymer containing an α-olefin having 4 to 8 carbon atoms and having a Mooney viscosity of 10 to 100 measured at 100 ° C. according to JIS K6300. And a flexural rigidity of 4,500 to 9,000 kg / c measured according to JIS K7106.
polyolefin resin foamed particles using a composition having a m of ² as a base resin.