JPH05140362A - Polyolefin resin expanded particles - Google Patents

Abstract

(57) [Summary] [Purpose] Excellent fusion properties even at low steam pressure.
Provided are polyolefin resin foamed particles suitable for producing a polyolefin resin foam having excellent cushioning performance and impact resistance. [Constitution] α containing an α-olefin having 4 to 8 carbon atoms
-Olefin / propylene copolymer 60 to 95% by weight
And 5 to 40% by weight of a polyolefin rubber having a Mooney viscosity of 10 to 100 and a bending rigidity of 4,500.
Polyolefin-based resin expanded particles having a base resin having a composition of about 9,000 kg / cm ² .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin foamed particle suitable for producing an in-mold foam molded article useful as a packaging container, toy, automobile bumper core material, helmet core material, packaging cushioning material, etc. Is.

[0002]

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

However, the polyolefin resin foam molded article has insufficient cushioning performance, and as a conventional method for improving the cushioning performance, a method for increasing the rigidity of the base resin of the foam, for example, in the case of polypropylene foam, A resin containing ethylene-propylene random copolymer having a low ethylene content as a base resin is used, or butene-1 is used as a copolymerization monomer of butene-1 in place of ethylene.
It has been proposed to use a propylene random copolymer (JP-A-1-242638).

[0004]

When a base resin having high rigidity, which has been proposed as a means for improving the cushioning performance, is used, the compressive strength of the foam, which is an index of the cushioning performance, certainly increases, and the foam is Since the energy absorption amount per unit volume of is increased, the performance as a cushioning material is improved. However, since all the base resins having high rigidity tend to have high crystallinity, there is a problem that the impact resistance is lowered and the steam pressure at the time of molding must be increased. For example, when the foamed molded product of the butene-1 / propylene random copolymer or propylene homopolymer is used as a cushioning material for packaging, the portion protecting the corner portion of the package is cracked by impact. However, it has a drawback that it does not exhibit sufficient buffering performance. It is considered that this is due to the low impact resistance of the foamed molded product and the weak fusion during molding. Therefore, the base resin having high rigidity is limited in terms of design and design as a cushioning material, so that its use is limited.

On the other hand, conventionally, as a polyolefin resin foam excellent in impact resistance, an in-mold foam molding using a low crystalline polypropylene copolymer (Japanese Patent Laid-Open No. 60-110).
Nos. 431 and 60-110734) and in-mold foam moldings using linear polyethylene have been proposed (Japanese Patent Publication No. 60-00777 and Japanese Patent Publication No. 59-187).
No. 036, No. 64-1741, and No. 64-29.
No. 444). Certainly, these foamed molded products are more flexible than the highly crystalline polypropylene-based foamed molded products,
Although it has excellent impact resistance, it has a low compressive strength, and it is necessary to set a large density in order to obtain the same cushioning characteristics as that of a polypropylene-based foamed molded product, which leaves a problem in terms of weight reduction.

In the present invention, a foamed particle capable of producing a polyolefin resin in-mold foam molded article having a low density, an excellent cushioning performance, a large impact resistance, and an excellent fusion property even under a low steam pressure is provided. The purpose is to provide. Since this in-mold foamed article is excellent not only in cushioning performance but also in impact resistance, it can be used in a wide range of applications without being restricted by design aspects in cushioning design.

[0007]

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

In the present invention, as the α-olefin as a raw material of the α-olefin / propylene copolymer as the first component, butene-1, pentene-1, octene-1, 4-
A monomer having 4 to 8 carbon atoms such as methylpentene-1 is used, and one obtained by copolymerizing one or more of these with propylene is used. The 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 preferable.

JIS K which is the second component in the present invention
The Mooney viscosity measured at 100 ° C according to 6300 is 1
Examples of the polyolefin rubber having 0 to 100 include α-, such as ethylene, propylene, butene-1, and pentene-1.
It is a low crystalline or amorphous rubbery copolymer obtained by randomly copolymerizing two or more kinds of olefin monomers. Further, this polyolefin rubber may be a copolymer of 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 beads is not improved, and when it exceeds 100, the impact resistance of the obtained foamed product is not sufficiently improved. The Mooney viscosity of the polyolefin rubber according to the present invention is JIS K63.
No. 00, using an L-type rotor at a test temperature of 100 ° C. for a preheating time of 1 minute and a rotor operating time of 4 minutes.

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,
Bending rigidity 4,500-9,000 kg / cm measured according to JIS K7106 by mixing polyolefin rubber having a Mooney viscosity of 10-100 at a ratio of 5-40% by weight, preferably 5-30% by weight. The composition of ² is used as a base resin for expanded beads. In this case, if the bending 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 bending rigidity is 9.0
When it exceeds 00 kg / cm ² , the impact resistance is low and not practical.

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

[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, etc. may be mixed with this composition (base resin), if necessary. it can. The amount to be mixed is determined in consideration of economy and required quality, but is generally 5% by weight or less, preferably 2% by weight or less with respect to the base resin. In the present invention, solid mixing by kneading is generally used for producing the composition. For example, kneading using a screw type extruder, Banbury mixer, mixing roll, etc.,
After kneading, it is granulated into a granule with an appropriate size. In this case, any method such as a strand cutting method, an underwater cutting method, a sheet cutting method, a freeze crushing method, and a melt spraying method may be used.

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, air, nitrogen gas,
Inorganic gases such as carbon dioxide can also be used. The amount of the volatile expanding agent added varies depending on the type of the expanding agent and the intended bulk density of the resin particles, but usually the resin particles 1
It is 10 to 80 parts by weight with respect to 00 parts by weight.

As the dispersant for dispersing the 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 and sodium dodecylbenzenesulfonate as a suspension aid in combination. This fine tricalcium 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 is 100 to 1,000 parts by weight, preferably 2 parts by weight, relative to 100 parts by weight of the resin particles.
It is from 00 to 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.
If it exceeds 1,000 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.

The expanded 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 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 foamed particles to each other and then the mold is cooled to obtain a product. A method for obtaining a product by pre-impregnating expanded particles with a volatile liquid expanding agent to give secondary expanded ability to the expanded particles, then filling the mold, heating with steam to perform secondary expansion, and fusing the 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
A method of obtaining a product by subsequent foaming and fusing particles together (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 the atmospheric pressure and then heating with steam to fuse the foamed particles together, and the formula of the foamed particles at that time

[0019]

[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)]
A method of controlling the compression ratio represented by the formula (40) to 70% (Japanese Patent Laid-Open No. 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%). Expanded particles themselves are filled with expanded particles having secondary expansion ability in a mold cavity under normal pressure, or in a mold under pressure and heated by steam for secondary expansion and fusion of particles. Method for obtaining product (Japanese Patent Laid-Open No. 62-128)
No. 709, No. 63-256634, No. 63-2589.
39, 63-107516).

Any of the above 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.

[0022]

[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 tank, and then cut into a base resin having a size of about 1.8 mg / grain. Created particles. The flexural rigidity of this 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 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 supplied into the closed container, heated to 138 ° C. over 1 hour, and kept at the same temperature for 15 minutes. The internal pressure of the autoclave 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, the temperature of the closed container should be kept at 13 ° C during the discharge of the dispersion liquid.
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 size was 200 μm. Further, blocking of the foamed particles was not observed.

The foamed particles were left to dry in a room at 40 ° C. for 2 days and then dried in a 2 m ³ pressure vessel at 2 kg / cm ² G
When pressure-aged for 24 hours with pressurized air, the internal pressure of the expanded beads was 0.3 kg / cm ² G. Then, the particles were filled in a mold having a steam hole, and the pressure was 2.5 kg / cm.
Guide ² G steam, heat and melt the foamed particles,
Then, after cooling with water 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 size of 00 mm, a width of 900 mm, and a thickness of 50 mm, and had few surface gaps and no irregularities. Further, when it was broken from the center of the molded product, about 95% 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, 25 mm thick sample for compression test and 40 m in height
m, lateral 200 mm, and thickness 20 mm samples for impact resistance test were obtained by cutting 5 points and 20 points, respectively. The compression test conforms to NDS-Z0504, compression speed 10 mm
The stress at 50% compression was evaluated as the compressive strength. Moreover, the impact resistance test is performed according to JIS K7211.
According to the above method, 255 g of steel balls were dropped and the 50% fracture height H ₅₀ was evaluated according to the following formula.

[0027]

[Equation 3]

H ₅₀ : 50% fracture height (cm) H ₁ : test height (cm) when height level (i) is 0 d: height interval (cm) when test height is raised or lowered 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 test pieces that were destroyed (or not destroyed) (N = Σn _i ) ± 1/2: Negative sign was used when the destroyed data was used, and data that was not destroyed was used Take the right time.

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

[Examples 2 to 6 and 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 resin shown in Table 1 was used as the resin particles.

[0031]

EFFECT OF THE INVENTION The expanded beads of the present invention are excellent in fusion property even under a low steam pressure, and a molded article molded using the expanded particles has a low density, a high compressive strength, and an excellent impact resistance. Can be used in.

[0032]

[Table 1]

[0033]

[Table 2]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromi Yamanaka 1000, Kawajiri-cho, Yokkaichi-shi, Mie Prefecture

Claims (1)

[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 a Mooney viscosity of 10 to 100 measured at 100 ° C. according to JIS K6300. It is composed of 5 to 40% by weight of system rubber and has a bending rigidity of 4,500 to 9,000 kg / c measured according to JIS K7106.
Polyolefin-based resin expanded particles whose base resin is the composition of m ² .