JP2001187824A - Extrusion-foamed board of mixture of polypropylene and polystyrene resins - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extrusion-foamed board of a polypropylene resin having a large thickness, a high closed cell rate and a lower density of a small average cell size. SOLUTION: An extrusion-foamed board is formed by mixing a resin mixture of (a) 50-95 pts.wt. of a polypropylene resin, (b) 50-5 pts.wt. of a polystyrene resin and (c) 0.5-15.0 pts.wt. based on to 100 pts.wt. of (a)+(b) of a hydrogenated styrene-isoprene block copolymer, a physical foaming agent and PTFE having low molecular weight of not more than 1 μm of the primary particle size using an extruder, followed by making it foam by compressed extrusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin extruded foam board. More particularly, the present invention relates to a polypropylene-based resin (for example, a modified polypropylene-based resin) extruded foam board that can be suitably used for a structural material such as a wall of a building, a floor partition, and a heat insulating material.

[0002]

2. Description of the Related Art A foam made of a thermoplastic resin is generally used widely as a heat insulating material, a cushioning material, a core material, a food container, etc. because of its light weight and good heat insulating property and buffering property of external stress. ing.

[0003] Foams using a polyolefin-based resin as a base resin are mainly used for low-density polyethylene, but the polyethylene-based resin has a drawback of insufficient heat resistance. On the other hand, polypropylene resin
Because of its high elasticity and excellent solvent resistance, heat resistance, and hinge properties, it can be expected to have a very wide range of applications when foams are manufactured. Since the strength of the wall is not sufficiently maintained, it is extremely difficult to produce a thick foam such as a polyethylene resin.

[0004] In an attempt to overcome such difficulties,
A foaming method using polypropylene having a high melt tension is disclosed in JP-A-53-43766 and JP-A-57-19.
No. 7132, JP-A-4-363227, and the like. However, satisfactory foam boards have not yet been obtained using these methods.

In recent years, there has been reported a method for producing a sheet-like foam using polypropylene having a long-chain branched structure as disclosed in JP-T-5-506875. However, only a thin foam having a thickness of less than 10 mm can be produced by the above-mentioned method, and a foam having good impact resistance and cushioning property cannot be obtained with the occurrence of corrugations and voids.

Japanese Patent Application Laid-Open No. 8-504471 discloses a foaming factor F (foam density × average cell diameter × tan δ).
^Although a propylene foam of ^0.75 ) <1.8 is disclosed, there is a drawback in that a special method of converging foam with a porous die makes it possible to obtain a thick foam only with a foam having a defective quality. .

Japanese Patent Application Laid-Open No. 7-252318 discloses a resin for a thick-walled polypropylene resin extruded foam having a prescribed biaxial elongational viscosity. However, this resin has an Mz containing an ultrahigh molecular weight component of 8 × 10 ⁶ or more,
/ Mw is a special linear polypropylene resin having a value of 10 or more, and the disclosed production method is a special method of two-stage polymerization.

On the other hand, as a foam of a mixed resin of polyolefin and polystyrene, a foam of a mixture using a hydrogenated styrene-butadiene block copolymer as a compatibilizer is disclosed in JP-A-50-32263. Have been. However, this publication only describes polyethylene as a polyolefin and does not describe polypropylene.

Japanese Patent Application Laid-Open No. Sho 62-174237 discloses a polyolefin and polystyrene using a special hydrogenated styrene-butadiene block copolymer in which the amount of 1,2-bonded butadiene and the amount of styrene are specified. A mixed resin foam is disclosed. In this publication, an example in which polypropylene is used as a polyolefin is also disclosed.
Only about foam is obtained.

It is also known to use polytetrafluoroethylene (hereinafter abbreviated as PTFE) as an additive during foaming. JP-B-46-19191 and JP-A-2-279739 disclose the use of a thermoplastic resin as a foam cell nucleating agent. In addition, Japanese Patent Application Laid-Open
No. 138403 discloses that a low molecular weight PTFE having an average particle diameter of 5 to 40 μm is used as a foam cell nucleating agent of a thermoplastic resin.
Polyethylene terephthalate thickened with pyromellitic dianhydride, and polypropylene is not disclosed. This is because, as described above, ordinary polypropylene has a low foaming suitability, and a foamed board cannot be made using the PTFE disclosed herein.

As described above, there has been found a method for producing a low-density foam having a large thickness, a high closed cell ratio and a small average cell diameter by extrusion foaming by improving the foaming property of the polypropylene resin. There is no present.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-density extruded polypropylene resin foam board having a large thickness, a high closed cell ratio and a small average cell diameter.

[0013]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that a polypropylene resin, a polystyrene resin, and hydrogenated styrene-
In a process of mixing an isoprene block copolymer (hereinafter referred to as SEPS) with a physical foaming agent with an extruder, and extruding and foaming to produce an extruded foam board, a low molecular weight having a primary particle diameter of 1 μm or less. By using PTFE, it was finally found that an extruded foam board having a large thickness, a high closed cell ratio, a low density, and a small average cell diameter was obtained, and completed the present invention.

That is, in the present invention, (a) 50 to 95 parts by weight of a polypropylene resin, (b) 50 to 5 parts by weight of a polystyrene resin, and (c) SEPS to (a) +
(B) a mixed resin obtained by mixing 0.5 to 15.0 parts by weight with respect to 100 parts by weight, a physical foaming agent, and (a) + (b) 10
An extruded foam board obtained by mixing an extruder with 0.01 to 0.5 parts by weight of low molecular weight PTFE having a primary particle diameter of 1 μm or less with respect to 0 part by weight, extruding and foaming ( The extruded foam board according to claim 1, wherein the polypropylene-based resin is a modified polypropylene-based resin obtained by modifying a linear polypropylene-based resin by a reaction with an isoprene monomer and a radical polymerization initiator. 2) The extruded foam board (Claim 3) according to claim 1, wherein the secondary aggregated particles of polytetrafluoroethylene have an average particle diameter of 1 to 20 µm, and a density of 50 to 10 kg /.
m ³ , thickness 20 mm or more, closed cell rate 60% or more,
The extruded foam board according to claim 1, which has an average cell diameter of 1.0 mm or less (claim 4).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In order to obtain a low-density polypropylene resin extruded foam board having a large thickness, a high closed cell rate, and a small average cell diameter from a polypropylene resin, foaming in a die is suppressed and foaming initial time is reduced. It is important to effectively generate bubble nuclei.

A foam board can be produced by extrusion foaming using a physical foaming agent and a mixed resin obtained by mixing a polypropylene resin, a polystyrene resin and SEPS, but the primary particle diameter is 1 μm or less. By using the low-molecular-weight PTFE together, it is possible to easily achieve both a high closed cell ratio and a small average cell diameter. Extrusion foaming can be performed, for example, by mixing a mixed resin, a physical foaming agent, and PTFE with an extruder and extruding the mixture into a low pressure zone.

Further, as the polypropylene resin, a homopolypropylene, a random or block copolymer containing 75% by weight or more, preferably 90% by weight or more of a propylene component, or a modified polypropylene resin obtained by modifying these may be used. it can. As the polypropylene-based resin, one or more polypropylene-based resins can be used.

The modified polypropylene resin is, for example,
A method of irradiating an unmodified linear polypropylene resin with radiation, or an unmodified polypropylene resin containing one or more monomers and one or more radical polymerization initiators It can be obtained by a method of adding and melt-mixing.

The linear polypropylene resin used in the modified polypropylene resin is a homopolymer or a copolymer of propylene, particularly a block copolymer or a random copolymer, and a crystalline polymer. can give. As the propylene copolymer, 7
Those containing 5% by weight or more, especially 90% by weight or more, are characterized by the crystallinity, rigidity,
It is preferable because chemical resistance and the like are maintained.

Examples of the copolymer of propylene include a copolymer of α-olefin and propylene. Examples of the copolymerizable α-olefin include ethylene, butene-1, isobutene, pentene-1,3-methyl-butene-1, hexene-1, 4-methyl-pentene-1,3,4-dimethyl-butene- 1, heptene-1,
3-methyl-hexene-1, octene-1, decene-1
Α-olefins having 2 or 4 to 12 carbon atoms such as cyclopentene, norbornene, 1,4,5,8-dimethano-1,2,3,4,4a, 8,8a-6-octahydronaphthalene Olefin; 5-methylene-2-
Norbornene, 5-ethylidene-2-norbornene,
Dienes such as 1,4-hexadiene, methyl-1,4-hexadiene, 7-methyl-1,6-octadiene;
Vinyl chloride such as vinyl chloride, vinylidene chloride, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, maleic acid, ethyl acrylate, butyl acrylate, methyl methacrylate, maleic anhydride, styrene, methylstyrene, vinyltoluene, divinylbenzene, etc. One or two or more such as a monomer. Of these, ethylene and butene-1 are preferred in that they are inexpensive.

The shape and size of the polypropylene resin are not limited, and may be powder or pellets.

Examples of the monomer include isoprene,
Styrene, 1,3-butadiene and the like can be used.

The polypropylene resin used in the present invention is preferably a modified polypropylene resin obtained by reacting a linear polypropylene resin, isoprene, and a radical polymerization initiator.

The amount of isoprene to be added is 0.01 to 50 parts by weight, especially 0.1 to 5 parts by weight, per 100 parts by weight of the linear polypropylene resin. It is preferable because the characteristics such as impact resistance and chemical resistance are maintained.

A monomer copolymerizable with isoprene;
For example, styrene, methyl styrene, vinyl toluene,
Vinyl monomers such as chlorostyrene, chloromethylstyrene, bromostyrene, fluorostyrene, nitrostyrene, vinylphenol, divinylbenzene, isopropenylstyrene; vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, acetic acid Vinyl, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, metal acrylate,
Acrylates such as metal methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate;
Methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and stearyl methacrylate may be used together with isoprene in an equal amount or less.

The radical polymerization initiator generally includes a peroxide, an azo compound and the like. It is desirable that a graft reaction occurs between the linear polypropylene-based resin and the isoprene monomer. For that purpose, a radical polymerization initiator having a so-called hydrogen abstraction ability is preferable, and in general, ketone peroxide, peroxyketal, and Organic peroxides such as peroxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyesters and the like can be mentioned. Among them, those having high hydrogen extraction ability are particularly preferable.
For example, 1,1-bis (t-butylperoxy) 3,
3,5-trimethylcyclohexane, 1,1-bis (t
-Butylperoxy) cyclohexane, n-butyl 4,
4-bis (t-butylperoxy) valerate, 2,2
Peroxy ketals such as -bis (t-butylperoxy) butane, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane,
α, α′-bis (t-butylperoxy-m-isopropyl) benzene, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,
Dialkyl peroxides such as 5-di (t-butylperoxy) hexine-3; diacyl peroxides such as benzoyl peroxide; t-butylperoxyoctate, t-butylperoxyisobutyrate, t-
Butyl peroxy laurate, t-butyl peroxy 3,5,5-trimethylhexanoate, t-butyl peroxyisopropyl carbonate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-butyl One or more kinds of peroxyesters such as peroxyacetate, t-butylperoxybenzoate, di-t-butylperoxyisophthalate and the like can be mentioned.

The radical polymerization initiator is added in an amount of 0.05 to 1 based on 100 parts by weight of the polypropylene resin.
0 parts by weight, particularly 0.1 to 5 parts by weight, is preferable in that the excessive decrease in the melt viscosity of the modified polypropylene-based resin is suppressed, and it is economical.

Further, if necessary, an antioxidant, a metal deactivator, a phosphorus-based processing stabilizer, an ultraviolet absorber, an ultraviolet stabilizer, a fluorescent brightener, a metal soap, or the like, as long as the effects of the present invention are not impaired. Stabilizers such as antacid adsorbents; crosslinking agents, chain transfer agents,
Additives such as a nucleating agent, a lubricant, a plasticizer, a filler, a reinforcing material, a pigment, a dye, a flame retardant, and an antistatic agent may be used.

As a device for reacting a linear polypropylene resin, a monomer (for example, isoprene) and a radical polymerization initiator, rolls, co-kneaders, Banbury mixers, Brabenders, single-screw extruders, twin-screw extruders And horizontal agitators such as a kneader, a two-shaft surface renewing machine, and a two-shaft multi-disc device, and a vertical agitator such as a double helical ribbon agitator. Of these, extruders are particularly preferred from the viewpoint of productivity.

The order and method of mixing and kneading (stirring) a linear polypropylene resin, a monomer (for example, isoprene) and a radical polymerization initiator are not particularly limited. After mixing a linear polypropylene resin, a monomer (eg, isoprene) and a radical polymerization initiator, melt kneading (stirring)
Alternatively, after the polypropylene resin is melt-kneaded (stirred), a monomer (for example, isoprene) or a radical polymerization initiator may be mixed simultaneously or separately, collectively or separately.

The temperature of the kneading (stirring) machine is 130 to 400 ° C.
However, it is preferable in that the polypropylene resin melts and does not thermally decompose. The time is generally 1 to 60 minutes.

As described above, a modified polypropylene resin can be produced.

The polystyrene resin used in the present invention is preferably a styrene homopolymer, and α
-A copolymer containing styrene as a main component with a monomer copolymerizable with styrene such as methylstyrene, acrylonitrile, butadiene, and methyl methacrylate, or a mixture thereof.

The melt flow rate of the polystyrene resin is 0.5 to 20 g / 10 minutes (200 ° C. × 5K
The range of g) is preferred.

The SEPS used in the present invention is also known, and is a hydrogenated styrene-isoprene block copolymer. The ratio of the styrene component is 20 to 70
% By weight is preferred. Further, it is preferable that the double bond of the block copolymer is hydrogenated by 90% or more with respect to the entire double bond portion.

Next, in the present invention, as a method of mixing and foaming a composition comprising PTFE and a mixed resin obtained by mixing the polypropylene-based resin, polystyrene-based resin and SEPS, for example, the mixed resin is mixed with PTFE.
E is preliminarily blended, a physical foaming agent is press-fitted under high temperature and high pressure and mixed, cooled to an appropriate foaming temperature, and extruded under atmospheric pressure.

The resin mixture is obtained by uniformly blending pellets or powders of the respective component resins by a blender, by once passing through a kneading extruder and melt-blending, or by mixing a polystyrene resin and SEPS. Melt blending, followed by dry blending with a polypropylene resin.

Preferred physical blowing agents in the present invention include, for example, aliphatic hydrocarbons such as propane, butane, isobutane, pentane, hexane and heptane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; chlorodifluoro Halogenated hydrocarbons such as methane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloroethane, dichlorotrifluoroethane, dichlorotetrafluoroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, and perfluorocyclobutane; Species or two or more species. Among them, aliphatic hydrocarbons are preferable, and isobutane is particularly preferable.

The amount of the foaming agent is selected depending on the type of the foaming agent and the target expansion ratio.
1 to 100 parts by weight per 0 parts by weight is preferred. If the amount of the foaming agent is small, the density of the foam tends to increase, and if it is large, the thickness tends to decrease.

The primary particle size is 1 μm or less (preferably 1 μm
m)), the average particle diameter of particles secondary aggregated with a low molecular weight type fine powder for a lubricant is 1 to 20 μm.
Are preferred. Nucleating effect tends to be small in high molecular weight PTFE and PTFE having a large primary particle diameter.

The amount of PTFE to be added is selected depending on the type of foaming agent used in combination and the target average cell diameter.
Generally, 0.01 to 0.1 parts by weight per 100 parts by weight of the resin mixture.
It is preferable to add so as to be 5 parts by weight. If the amount of PTFE is small, the nucleation effect tends to be small, and if it is large, the thickness of the foam tends to be small.

In order to further control the bubble diameter, a known foam nucleating agent such as mica, talc, or sodium bicarbonate-organic acid may be used in combination, if necessary.

[0043]

Next, the foamed board according to the present invention will be described based on examples and comparative examples, but the present invention is not limited to only these examples.

The density, closed cell ratio and average cell diameter of the obtained extruded foam board were measured by the following methods, and the appearance was visually evaluated according to the following evaluation criteria. Density of foam board: Calculated from weight and volume obtained by submersion method. Closed cell ratio: Measured using a multi-pycnometer (product name, manufactured by Yuasa Ionics Co., Ltd.) according to ASTM D-2856. Average cell diameter: The cell chord length on the straight line in the thickness direction, width direction, and extrusion direction at the center of the foam board is measured, and multiplied by 1.626 to show the average in three directions. Bubble diameter = 1.626 × Bubble chord length on straight line Evaluation criteria for appearance: ：: No unfoamed part, fluff and wrinkles are observed. X: Unfoamed parts, fluff, and wrinkles are seen.

Example 1 Ethylene random polypropylene (Mitsui Petrochemical Co., Ltd.)
Manufactured by Hypol B230, MI = 0.5 at 230 ° C.
1,1-bis (t-butylperoxy) is used as a radical generator with respect to 100 parts by weight of ethylene content (3% by weight).
3,3,5-trimethylcyclohexane (manufactured by NOF CORPORATION, perbutyl 3M, 1 minute half-life temperature 147
C.) 0.5 part by weight, and mixed and stirred for 10 minutes using a ribbon blender. 50 Kg of this mixture was fed from a hopper of a twin screw extruder (TEX44) manufactured by Japan Steel Works, Ltd.
/ H, and 2.5 parts by weight of an isoprene monomer (manufactured by Wako Pure Chemical Industries, Ltd., special grade) was supplied at a rate of 1.25 kg / h (propylene 2.5 parts by weight with respect to 100 parts by weight of the homopolymer). The obtained rod-shaped modified polypropylene resin having a diameter of about 4 mm was water-cooled and chopped to a thickness of 3 mm to obtain pellets of the modified polypropylene resin.

The twin-screw extruder was of the same-direction twin-screw type, had a cylinder hole diameter of 44 mmφ, and had a maximum effective screw length (L / D) of 38.

The resulting modified polypropylene-based resin was
Parts by weight, polystyrene (Stylon G, manufactured by Asahi Kasei Corporation)
9305, MFR1.5) and SEPS (manufactured by Kuraray Co., Ltd., Septon 2104: styrene content 65)
% By weight) and a PT having a primary particle diameter of 0.3 μm.
After dry-blending 0.1 part by weight of FE (Lubron L-2: manufactured by Daikin Industries, Ltd., the average particle diameter of secondary aggregated particles is about 4 μm) using a ribbon blender, the mixture is mixed with 5 parts by weight.
The mixture is fed to a 65 mm-90 mm tandem extruder at 0 kg / h and plasticized at 200 ° C. in a first stage extruder (65 mm).
12 parts by weight with respect to parts by weight, and the second-stage extruder (90
mm) to cool the resin temperature to 140 ° C,
Slit width 40mm, slit thickness 3.0mm, land 2
It was extruded from a 5 mm rectangular die and passed through a molding die directly connected to the rectangular die to obtain a foam board. Table 1 shows the physical properties of the foam board.

Example 2 0.05 parts by weight of TLP-10F-1 (primary particle diameter: 0.2 μm, average secondary particle diameter: about 3 μm) manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd. as PTFE A foam board was obtained in the same manner as in Example 1 except that the foam board was used.
Table 1 shows the physical properties of the obtained foam board.

Example 3 As PTFE, 0.1 part by weight of MP-1500J (primary particle diameter: 0.2 μm, average particle diameter of secondary aggregated particles: about 20 μm) manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd. was used. Otherwise, a foam board was obtained in the same manner as in Example 1. Table 1 shows the physical properties of the obtained foam board.

Example 4 As PTFE, Lubron L-5 manufactured by Daikin Co., Ltd. (primary particle diameter: 0.2 μm, average particle diameter of secondary aggregated particles: about 7)
μm) was used in the same manner as in Example 1 except that 0.1 parts by weight of the foamed board was obtained. Table 1 shows the physical properties of the obtained foam board.

Comparative Example 1 A foam board was obtained in the same manner as in Example 1 except that 0.2 parts by weight of talc was added instead of PTFE. Table 1 shows the physical property values of the obtained foam board.

Comparative Example 2 A foam board was obtained in the same manner as in Example 1, except that talc was added in an amount of 1.0 part by weight instead of PTFE. Table 1 shows the physical property values of the obtained foam board.

[0053]

[Table 1]

The foam board obtained in the example has a high closed cell ratio and a small average cell diameter, whereas the foam board obtained in the comparative example has both a high closed cell ratio and a small average cell diameter. It turns out to be difficult.

[0055]

According to the present invention, a foam board which can be suitably used as a heat insulating material can be easily provided because the thickness is large, the closed cell ratio is high, the average cell diameter is small, and the density is low. be able to.

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Claims (4)

[Claims] (1) A polypropylene resin is used in an amount of 50 to 9:
5 parts by weight, (b) 50 to 5 parts by weight of a polystyrene resin, and (c) 0.5 to 15 parts by weight of hydrogenated styrene-isoprene block copolymer with respect to 100 parts by weight of (a) + (b). 0.0 parts by weight of the mixed resin, the physical foaming agent, and 0.01 to 100 parts by weight of (a) + (b).
An extruded foam board obtained by mixing 0.5 part by weight of polytetrafluoroethylene having a primary particle diameter of 1 μm or less with an extruder, extruding and foaming. 2. The extruded foam board according to claim 1, wherein the polypropylene resin is a modified polypropylene resin obtained by modifying a linear polypropylene resin by reaction with an isoprene monomer and a radical polymerization initiator. 3. The extruded foam board according to claim 1, wherein the secondary aggregated particles of polytetrafluoroethylene have an average particle size of 0.5 to 20 μm. 4. A density of 50 to 10 kg / m ³ and a thickness of 2
The extruded foam board according to claim 1, which has a closed cell ratio of 60% or more and an average cell diameter of 1.0 mm or less.