JP3349749B2 - Polypropylene resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foam having excellent chemical resistance, solvent resistance, high closed cell ratio, high strength and high expansion ratio, which is used in known fields such as cushioning materials and structural materials. .

[0002]

2. Description of the Related Art With respect to a foam of a composition of a polyolefin resin and a polystyrene resin, a foam of polyethylene and polystyrene having substantially the same foaming temperature is disclosed in
121669, JP-B-59-14493, JP-B-60-
1338, Japanese Patent Publication No. 4-12737 and the like disclose that a good foam can be obtained.

However, foams of polypropylene and polystyrene compositions having different foaming temperatures are disclosed in
Although disclosed in -40166, the preferred polyolefin is described as being polyethylene. Japanese Patent Publication No. 3-33186 discloses a foam of a composition in which soft polypropylene is impregnated with polystyrene, and Japanese Patent Application Laid-Open No. 4-258645 discloses a foam of a syndiotactic polypropylene and a polystyrene composition. However, heat resistance and high rigidity, which are inherent characteristics of polypropylene, cannot be exhibited.

In Japanese Patent Publication No. 57-37188, a foam made of a composition of polypropylene and polystyrene utilizes the fact that cells partially break to generate many open cells. However, there is a problem in strength.

[0005]

That is, at present, a foam of a polypropylene and polystyrene composition having the effects of heat resistance, high strength, and high expansion ratio has not been obtained.

[0006]

In order to solve the above problems, various methods have been studied. As a result, by adding a polyphenylene ether resin to a polystyrene resin,
It has been found that the foaming temperature can be made substantially equal to the foaming temperature of the polypropylene-based resin, and a foam having a high closed cell ratio, high strength and high expansion ratio can be obtained, and the present invention has been accomplished.

That is, the present invention comprises (a) a polypropylene resin, (b) a polystyrene resin, (c) a polyphenylene ether resin, and (d) a styrene elastomer, wherein (a) is 95 to 51% by weight, (B) and (c)
Is 5 to 49% by weight, and (c) / ((b) +
(C)) = resin in the range of 0.1 to 0.8 ((a) +
(B) + (c)) For 100 parts by weight, (d) was added at 0.
1 to 50 parts by weight of a foam.

The polypropylene resin used as the component (a) in the present invention is not particularly limited as long as it is a polymer obtained by polymerizing a propylene monomer as a main component, and propylene and ethylene, 1-butene, 4-methyl-1-pentene, etc. Or a random or block copolymer with another α-olefin, or a mixture of these copolymers. Also, ethylene, 1-butene, 4-methyl-1
-Among α-olefins such as pentene, a polymer consisting of a copolymer of two or more of two or more kinds and propylene, or a mixture of these polymers may be used.

However, among these, propylene homopolymer is particularly preferred, and can be used without any limitation in crystallinity. The melt flow rate (MFR, AS
TMD1238, 230 ° C, 2.16 Kg load) is preferably 0.01 to 10.0 g / 10 min, and more preferably MFR is 0.1 to 5.0 / 10 min. If the MFR is below this range, melt-kneading is extremely difficult, and above this range the foamability is insufficient.

The polystyrene resin used as the component (b) in the present invention includes styrene homopolymer (GPPS), rubber-modified high impact polystyrene (HIPS), acrylonitrile-styrene copolymer (AS), and acrylonitrile-butadiene-styrene copolymer. The resin is composed of an aromatic vinyl compound such as a polymer (ABS), a methyl methacrylate-styrene copolymer, a conjugated diene-styrene block copolymer, and is preferably GPPS or HIPS, and particularly preferably GPPS. MFR (ASTM D123
(8, 230 ° C, 2.16 kg load) is 0.01 to 10.
0 g / 10 min is preferable, and MFR is more preferably 0.1 to 5.0 / 10 min. If the MFR is below this range, melt-kneading is extremely difficult, and above this range the foamability is not sufficient.

The polyphenylene ether resin used as the component (c) of the present invention (hereinafter simply referred to as PPE)
Is the bonding unit:

[0012]

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(Where R1, R2, R3, and R4
Are each selected from the group consisting of hydrogen, halogen, hydrocarbon, or substituted hydrocarbon, and may be the same or different. ), Reduced viscosity (0.5 g / dl, chloroform solution, measured at 30 ° C.)
Is in the range of 0.15 to 0.70, more preferably 0.1 to 0.70.
Homopolymers and copolymers in the range of 02 to 0.60. As a specific example of this PPE, poly (2,6-
Dimethyl-1,4-phenylene ether), poly (2-
Methyl-6-ethyl-1,4-phenylene ether),
Poly (2-methyl-6-phenyl-1,4-phenylene ether), poly (2,6-dichloro-1,4-phenylene ether) and the like, and 2,6-dimethylphenol and other phenols (for example, 2, And 3,6-trimethylphenol and 2-methyl-6-butylphenol). Among them, poly (2,6-dimethyl-1,
4-phenylene ether) and a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol are preferred, and poly (2,6-dimethyl-) is particularly preferred.
1,4-phenylene ether).

The MFR (ASTM D1238, 230 ° C., 2.50 ° C.) of a composition obtained by melt-kneading the components (b) and (c).
16 kg load) is preferably 0.01 to 10.0 g / 10 min, and more preferably the MFR is 0.1 to 5.0 / min.
10 minutes. If the MFR is below this range, melt-kneading is extremely difficult, and above this range the foamability is not sufficient.

The above (a) polypropylene-based resin,
The blending ratio of (b) polystyrene resin and (c) polyphenylene ether resin is such that (a) is 95 to 51% by weight based on the total amount of (a) + (b) + (c), and (b) +
(C) is 5 to 49% by weight, and (c) / ((b) +
(C)) = 0.1 to 0.8. Preferably, (a)
90-55% by weight, (b) + (c) 10-45% by weight, and (c) / ((b) + (c)) = 0.2-0.
5 If the component (a) exceeds 95% by weight, no improvement in rigidity is observed, and if it is less than 51% by weight, the solvent resistance becomes poor. If the amount of the component (c) is out of the range defined in the claims, the foaming property becomes extremely poor.

The styrenic elastomer used as the component (d) in the present invention has at least one aromatic vinyl compound polymer block (A) and at least one conjugated diene polymer block (B), A hydrogenated block copolymer having a bonded aromatic vinyl compound content of 15 to 85% by weight and at least 70% of double bonds of a conjugated diene portion being hydrogenated, having the following structure.

[0017]

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Aromatic vinyl compound polymer block (A)
Is a polymer composed of styrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinylanthracene or a mixture thereof, and is preferably a styrene homopolymer or α-methylstyrene. And a styrene homopolymer is particularly preferred.

The conjugated diene polymer block (B) has 1,
3-butadiene, isoprene, 1,3-pentadiene,
3-butyl-1,3-octadiene, 4-ethyl-1,
It is a polymer composed of 3-hexadiene or a mixture thereof, or a polymer composed of a mixture of the above conjugated diene and an aromatic vinyl compound. Preferably, they are 1,3-butadiene and isoprene.

When the conjugated diene polymer block (B) is 1,3-butadiene, hydrogenation results in 1,4 butadiene.
Ethylene is generated from the portion polymerized by the bond, and butylene is generated from the portion polymerized by the 1,2 bond, to form an ethylene-butylene copolymer (SEBS). There is no particular limitation on the ethylene to butylene ratio of the ethylene / butylene copolymerized portion or the type of polymerization.

The number average molecular weight of the hydrogenated block copolymer is preferably 30,000 to 300,000, particularly preferably 60,000 to 100,000. If it is less than this range, the compatibilizing ability will be reduced, and if it is above this range, melt-kneading will be difficult. The proportion of the block (A) in the hydrogenated block copolymer is 15
-85% by weight, particularly preferably 50-70% by weight. If it is less than 15% by weight, the compatibilizing ability is insufficient, and
If it exceeds 5% by weight, the impact strength tends to decrease.

The hydrogenation rate of the double bond portion of the block (B) of the hydrogenated block copolymer is preferably 70% or more, more preferably 90% or more. 7
If it is less than 0%, the compatibilizing ability is insufficient. The amount of component (d) is 0.1 to 50 parts by weight, preferably 5 to 30 parts by weight, per 100 parts by weight of (a) + (b) + (c). If it exceeds 50 parts by weight, the rigidity is reduced.

The blowing agents used to obtain the foam of the present invention include, for example, carbon dioxide, hydrocarbons and halogenated hydrocarbons. Specific examples of the hydrocarbons include propane, butane, pentane, pentene, hexene and the like. However, specific examples of halogenated hydrocarbons include methyl chloride, trichloromonofluoromethane, dichlorodifluoromethane, monochlorotrifluoromethane, dichloromonofluoromethane, monochlorodifluoromethane, trichlorotrifluoroethane, dichlorotetrafluoroethane,
Monochloropentafluoroethane, monochlorodifluoroethane, tetrafluoroethane and the like can be mentioned. Further, two or more of these foaming agents may be used in combination.

The mixing ratio of the foaming agent is preferably in the range of 5 to 150 parts by weight, more preferably in the range of 7 to 100 parts by weight, and more preferably less than 5 parts by weight per 100 parts by weight of the resin. When the amount exceeds 150 parts by weight, the effect of increasing the cross-sectional area of the foam decreases. If desired, commonly used cell nucleating agents can be included. Examples of the bubble nucleating agent include inorganic fine powders such as talc and silicon oxide, organic fine powders such as zinc stearate and calcium stearate, and fine powders capable of generating gas by heating such as citric acid and sodium hydrogen carbonate. Powder or the like is used. In addition, if necessary, inorganic fillers such as calcium carbonate, talc, glass fiber, glass beads, silica, whiskers, titanium oxide, aluminum hydroxide, ammonium hydroxide, antimony oxide, and organic fillers such as carbon black and carbon fiber. Agents and optional additives such as antioxidants, pigments, flame retardants, antistatic agents, lubricants, UV absorbers and the like. There are no particular restrictions on the types of fillers and additives as long as they are commonly used for blending plastics.

Also, melt kneading for controlling the flow characteristics using a radical generator such as an organic peroxide may be used. Further, in producing the polypropylene resin composition used in the present invention, the above-mentioned (a) polypropylene resin, (b) polystyrene resin, (c) PPE resin, and (d) styrene elastomer are melt-kneaded together. Good, but in this case, it is necessary to melt and knead under a temperature condition at which the PPE resin sufficiently melts. Therefore, thermal degradation of the resin other than the component (c) occurs, which is not preferable.

However, since polystyrene and PPE are completely compatible, the composition obtained by melt-kneading once can be melt-kneaded at almost the same temperature as polypropylene. Therefore,
The components (b) and (c) are kneaded at a high temperature, and
The components (a) and (d) may be blended and melt-kneaded at a low temperature. For example, in the process of continuously manufacturing with an extruder or the like,
(B) Polystyrene-based resin and (c) PPE resin are melt-kneaded at a barrel temperature of 260 to 320 ° C., and the temperature of the barrel is lowered to 180 to 250 ° C. in the middle, and (a)
A method in which the component (d) is added and melt-kneaded can be used. In this case, with respect to the total amount of (b) + (c), (b) 10 to 90% by weight of a polystyrene resin and (c) 90 to 10% by weight of a PPE resin are melt-kneaded in a high temperature portion, and in a low temperature portion, The components (a) and (d) may be added so as to have the composition ratio of the present invention.

Alternatively, the component (b) and the component (c) may be melt-kneaded at a high temperature, and then the component (a) and the component (d) may be melt-kneaded at a low temperature again. That is, (b) 10 to 90% by weight of a polystyrene resin and (c) 90 to 1 of a PPE resin.
0% by weight is melt-kneaded at 260-320 ° C, and PS / PP
A master batch of E was prepared, and this was again mixed with components (a) and (d) in the range of 180-2
Melt and knead at 50 ° C.

[0028]

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited by these examples. The following materials were used as the raw material resin and the foaming agent in each of Examples and Comparative Examples. [1] Polypropylene resin PP-: propylene homopolymer MFR (230 ° C, 2.16 kg load) = 0.5 g / 10 min PP-: propylene homopolymer MFR (230 ° C, 2.16 kg load) = 2.0 g / 10 minutes [2] Polystyrene resin PS-: Styrene homopolymer MFR (230 ° C., 2.16 kg load) = 1.4 g / 10 minutes PS-: Styrene homopolymer MFR (230 ° C., 2.16 kg load) = 11 g / 10 minutes [3] Polyphenylene ether-based resin PPE: obtained by the following method.

After the inside of a stainless steel reactor having an oxygen blowing part at the bottom of the reactor and having a cooling coil and a stirring blade inside is sufficiently replaced with nitrogen, 53.6 g of cupric bromide,
1110 g of di-n-butylamine and 2 parts of toluene
0-liter, n-butanol 16 liters, methanol 4 liters mixed solvent, 2,6-xylenol 8.7.
5 kg was dissolved and charged into the reactor. While stirring, oxygen was continuously blown into the reactor, and polymerization was performed for 180 minutes. In order to maintain the internal temperature at 30 ° C., water was circulated through the cooling coil during polymerization. After completion of the polymerization, the precipitated polymer was separated by filtration, and a mixed solution of methanol / hydrochloric acid was added to decompose the remaining catalyst in the polymer. A viscosity of 0.54) was obtained. [4] Hydrogenated block copolymer SEBS: Hydrogenated product of styrene-butadiene tetrablock copolymer Number average molecular weight 85,000 Bound styrene content 60% by weight Butylene content 35% Hydrogenation rate 95% [5] Foaming agent Diflon 142b ( 1-Chloro-1,1-difluoroethane) The foams in Examples and Comparative Examples were evaluated according to the following evaluation methods and criteria. [1] Closed cell rate Measured by an air pycnometer method described in ASTM D-2856. [2] Foam density According to JIS-K6767. [3] Expansion ratio Expansion ratio = resin density before expansion / foam density. [4] Solvent resistance After immersing in acetone at 23 ° C. for 24 hours, taking out and drying with a vacuum dryer, the mass loss rate is within 5%: ◎, within 10%: ○, within 20%: △, Dissolution: x.

[0030]

Examples 2-3 and Comparative Examples 1-6 In Comparative Examples 1 and 2, the above polypropylene, polystyrene, and PPE were prepared as shown in Table 1.
Was melt-kneaded with a 25 mmφ co-rotating twin-screw extruder (ZSK-25; manufactured by W & P), then cooled with water and cut to obtain a pellet-shaped resin composition.

In Examples 2 and 3 and Comparative Examples 3 to 6, the above polypropylene, polystyrene, PPE and SEBS were blended in the composition shown in Table 1 and a 25 mmφ co-rotating twin screw extruder (ZSK-25; manufactured by W & P) ) After melt-kneading,
A pellet-shaped resin composition obtained by cooling with water and cutting was used. A first extruder (30 mmφ <L / D = 30) having a foaming agent injection port in the cylinder and a second extruder (40 mmφ in diameter) having a cooling oil jacket in the cylinder
(L / D = 30) using an extruding foaming apparatus having a structure connected in series to a first extruder heated to a maximum of 220 ° C.
The pellet-shaped resin composition was supplied at a supply rate of 4 kg / hour, and a predetermined foaming agent was injected into a zone where the resin composition was melt-kneaded to prepare a foaming composition. This blowing agent was continuously supplied by a high-pressure pump at a ratio of 10 parts by weight to 100 parts by weight of the resin. The composition obtained in this way is supplied to the second extruder through a connecting pipe, where it is gradually cooled to the optimum foaming temperature, and this composition is extruded from a rod die attached to the tip of the second extruder, and foamed. I got a body. 2.0mm
Dies having 16 different diameters can be exchanged in increments of 0.2 mm from φ to 5.0 mmφ. Under the above extrusion conditions, the foaming behavior can be observed at a shear rate at the tip of the die of 170 to 2700 sec ⁻¹ .

In general, when the diameter of the die is increased under the condition of a constant discharge rate, the product cross-sectional area increases, but the resin pressure in the die decreases, and when the pressure reaches the limit pressure determined by the composition, foaming in the die occurs. However, the cross-sectional area of the product is drastically reduced, and the communication of air bubbles and the surface roughening are caused, so that the commercial value is significantly impaired. The evaluations in the experiments described below were all performed under the condition that the product area immediately before foaming in the die was maximized.

From these results, it has been clarified that the foam of the thermoplastic resin composition falling within the scope of the present invention is excellent in heat resistance, rigidity and oil resistance and has a very high closed cell ratio.

[0034]

[Table 1]

[0035]

Since the foam of the present invention is mainly composed of a polypropylene resin, a highly rigid foam excellent in solvent resistance, oil resistance, chemical resistance and heat resistance can be provided.

Claims (1)

(57) [Claims] 1. A composition comprising (a) a polypropylene resin, (b) a polystyrene resin, (c) a polyphenylene ether resin, and (d) a styrene elastomer, wherein (a) is 95 to 51% by weight and (b) The total of (c) is 5 to 49% by weight, and (c) / ((b) + (c)) = 0.1 to 0.
100 weight of resin ((a) + (b) + (c)) in the range of 8
Parts by weight of (d) in an amount of 0.1 to 50 parts by weight .