JPH02300240A - Production of expanded polyolefin - Google Patents

Abstract

PURPOSE:To expand a polyolefin uniformly without the necessity for irradiation in a high dose by irradiating an olefin molding containing an alkenylsilane/olefin copolymer and a blowing agent with a radiation and expanding the molding by heating. CONSTITUTION:An alkenylsilane/olefin copolymer of an MW of 10000-1000000, obtained by copolymerizing 0.001-30mol% alkenylsilane of formula I (wherein n is 0-12; p is 1-3; and R is a 1-12C hydrocarbon group) with an olefin of formula II in the presence of a Ziegler/Natta catalyst, is melt-mixed with 1-50wt.% blowing agent (e.g. azodicarbon-amide) and molded into a polyolefin molding of any desired shape. This molding is irradiated with a radiation (e.g. gamma-rays) in a dose of several tens of rads to several Mrads, and expanded by heating at a temperature higher than the decomposition temperature of the blowing agent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing foamed polyolefin. Preferably, after irradiating a molded article containing a polyolefin containing alkenylsilane in its main chain and a blowing agent,
The present invention relates to a method of producing foamed polyolefin by heating.

[Conventional technology]

Since polyolefin foam is lightweight and has a relatively good balance of physical properties, the 93a method for producing 8-foamed polyolefin, which is used in the world as insulation and cushioning materials, has conventionally used a low-boiling-point hydrocarbon compound as a foaming material. A method of foaming by heating and melting a mixture of a foaming material and a polyolefin under pressure and extruding it under normal pressure, or a method of foaming a mixture of a foaming material and a polyolefin using IF! Is it a synthetic form? Known methods include heating and crosslinking with 1' peroxide and foaming, or crosslinking with radiation and then heating and foaming. In particular, it is known that a method of forming the material with a T gland and then foaming produces a good foam because crosslinking can be performed at low temperatures and molding, crosslinking, and foaming can be performed separately.

(The invention attempts to solve this! IB) However, although crosslinking by radiation is easy to crosslink with polyethylene, etc., a crosslinking auxiliary agent is usually required, and in particular, for α-olefins such as propylene, compared with multi-tonal crosslinking auxiliary agents. There were problems such as the need to irradiate high-target radiation.

(Means for Solving the Problems) The present inventors have earnestly searched for a method for solving the above problems and producing foamed polyolefin 93a, and have completed the present invention.

That is, the present invention provides a foamed polyolefin, which is characterized by irradiating a polyolefin molded product containing an alkenylsilane-olefin copolymer and a foaming agent with radiation, and then foaming it by heating it to a temperature above the skin temperature at which the foaming agent decomposes. This is a manufacturing method.

In the present invention, the copolymer of alkenylsilane and olefin can be prepared by combining an olefin and a fulkenyl 7-lane using a so-called Ziegler-Natsuta catalyst consisting of a transition metal catalyst and an organometallic compound. An example is disclosed in No. .6f36. Furthermore, it may be a graft copolymer obtained by graft polymerization by heat treating a polyolefin with an alkenylsilane in the presence of a radical polymerization initiator such as peroxide. Those having a bond are preferably used, for example, the general formula 11gc=cl+-(C11g)a-5IHp
Examples include compounds represented by Rz-p (in the formula, n is 0 to 12, p is 1 to 3, and R is a hydrocarbon residue having 1 to 12 carbon atoms), and specific examples include vinylsilane, allyrunrane, butenylrunrane. , pentenyl, or compounds in which [I of 1 to 3 5L-H bonds of these heptads are substituted with chloro. Examples of olefins include compounds represented by the following formula: 1-1-2 o, c=co-R (in the formula, R is a hydrocarbon residue having 1 to 12 carbon atoms), and specific examples include ethylene, propylene, butene, etc. -12pentene-1
, hexene-1,2-methylpentene, heptene-1,
In addition to α-olefins such as octene-1, styrene or derivatives thereof are also exemplified.

In the present invention, for the copolymer of alkenylsilane on olefin, a catalyst consisting of T1Cl and triethylaluminum described in the above-mentioned US patent can also be used, but it is more preferable to use various highly active catalysts that have been developed since then and give polyolefins. is used.

In addition to the solvent method that uses an inert solvent as a polymerization method, bulk polymerization method and gas phase polymerization method can also be used. When titanium is used, an organoaluminum compound is preferably used as the organometallic compound.For example, titanium trichloride obtained by reducing titanium tetrachloride with metal aluminum, hydrogen, or organoaluminum is modified with an electron-donating compound. Titanium halide is supported on a catalyst system consisting of an organoaluminum compound and, if necessary, an electron-donating compound such as an oxygen-containing organic compound, or a jU form such as magnesium halide, or a product treated with an electron-donating compound. The obtained '& transfer metal compound catalyst organoaluminum compound, optionally a catalyst system consisting of an electron-donating compound such as an oxygen-containing a-organic compound, or a reaction product of magnesium chloride and alcohol is dissolved in a hydrocarbon solvent, Then, it is treated with a precipitant such as titanium tetrachloride to make it insoluble in a hydrocarbon solvent, and if necessary, it is treated with a ttt r-donating compound such as an ester or ether, and then treated with a titanium halide. Examples include catalyst systems comprising the resulting transition metal compound catalyst, an organic aluminum compound, and, if necessary, an electron-donating compound such as an oxygen-containing organic compound (for example, various examples are described in the following literature). Ziegler-NaL
Catalysts and Polyaeriz
aLlon by John Boar Jr.
(＾rademlc Press), Journal
or Macrosoricular 5ience
Reviews in Macro＊olecular
Chemistry and Phys: cs, C2
4(3) 355-385 (1984), same C25(1
) 578-597 (1985)).

Or i! which is soluble in hydrocarbon solvents! ! Polymerization can also be carried out using a catalyst consisting of a transfer metal catalyst and an aluminoxane.

As the electron-donating compound, oxygen-containing compounds such as ethers, esters, orthoesters, and alkoxy silicon compounds are generally preferred, and alcohols, aldehydes, water, and the like can also be used.

As the organic aluminium compound, trialkylaluminum, dialkylaluminum halide, alkylaluminum seth halide, and alkylaluminum civalide can be used. Examples of the /alkyl group include methyl group, ethyl group, propyl group, butyl group, hexyl group, etc. Examples include halides such as chlorine, bromine, and iodine. The aluminoxane is an oligomer polymer which can be IR-treated by reacting the organic aluminum with water or water of crystallization.

There is no particular restriction on the polymerization ratio of alkenylsilane and olefin, but from the standpoint of ln combination with polyolefin, alkenylsilane is usually 0.001 to 30%
It is about mol χ, preferably 0.1-10 mol χ. Further, when the copolymer is used alone without being mixed, the amount is preferably o, ooi to 5 mol 2.

There is no particular restriction on the molecular weight of the polymer, but it is preferably the same or lower than the molecular weight of the polyolefin used in the mixture.
The zero molecular weight that may be used after carrying out a molecular weight synthesis, molecular weight, etc.) is about 10,000 to 1,000,000.

There are no particular restrictions on the method of grafting alkenylsilane to polyolefin, and the methods and conditions used for ordinary graft copolymerization can be used. Usually, the method and conditions used for graft copolymerization are heated to a temperature higher than the decomposition temperature of the radical initiator in the presence of the polyolefin and alkenylsilane used. This allows easy graft copolymerization.

The polyolefin used in the present invention has the above general formula 1. Olefins represented by c=cH-R (wherein R is a hydrocarbon residue having 1 to 12 carbon atoms), specifically ethylene, propylene, butene-1, pentene-1, hexene-1,2-methyl Pentene, heptene-1, octene-
In addition to α-olefins such as 1, styrene or its derivatives are not only homopolymers but also random copolymers of each other, or the starting olefin alone or copolymerized with a small amount of other olefins, and then 2N or more Examples include so-called block copolymers produced by copolymerizing olefins. It is particularly effective to apply the method of the present invention to α-olefins such as propylene or copolymers thereof, which are difficult to crosslink when used alone. The production method for these polyolefins is already known and various brands are available on the market, and the method for producing the above-mentioned olefin and alkenylsilane polymer can be used, except that alkenylsilane is not used. Manufacturable.

In the present invention, the copolymer of alkenylsilane and olefin is usually mixed with a polyolefin that does not contain alkenylsilane, or only the copolymer of alkenylsilane is used without mixing polyolefin that does not contain alkenylsilane. I can do it. The proportion of copolymer of alkenylsilane and olefin used when mixed depends on the content of fulkenylsilane in the copolymer, but is it normal? The proportion of copolymer in the It compound is Q, 1wt%
It is preferable that the amount of alkenylsilane is about 0.005wLZ1 in the polyolefin when irradiated with radiation.
It is possible to use various known additives at the time of mixing, and there are no particular limitations.

Prior to crosslinking with radiation, the material is heated, melted and mixed with a foaming agent and molded into a desired shape. As the foaming agent to be used, any foaming agent whose decomposition point is higher than the above-mentioned molding temperature (and which decomposes to generate gas) can be used, and the gas generated is inert and easy to use. From this point of view, azo compounds such as azodicarbonamide are preferably used. The mixing ratio of the blowing agent varies depending on the characteristics of the blowing agent, but abdicarbonamide etc.
It is about 50-tχ, preferably about 1 to 40-tχ.

The polyolefin containing the above-mentioned blowing agent is molded into a desired shape and then subjected to a crosslinking reaction by irradiation with radiation.When carrying out the crosslinking reaction, it is possible to perform the crosslinking reaction in an inert gas atmosphere or in the presence of oxygen. You can choose the environment according to your needs.

The radiation used in the present invention includes α rays, β rays, T
Examples include rays, X, rays, and neutron beams, especially rklA,
ILF coson beams can be preferably used, and the irradiation dose is several +
It is a touch to irradiate from rad to several tens of Mrad,
Irradiation is carried out at a dose such that the degree of crosslinking is suitable for foaming.
Although it depends on the properties of the polyolefin or the degree of foaming, it is generally recommended that the degree of crosslinking be 10 to 902.

There are no particular restrictions on the irradiation temperature, and it may be below the heat-resistant temperature of the polyolefin and below the decomposition temperature of the blowing agent.
Normally, it is sufficient to carry out the reaction at room temperature.

The thus crosslinked molded product is heated to a temperature higher than the decomposition temperature of the foaming agent and foamed. The preferable temperature and time at this time vary depending on the characteristics of the polyolefin 4 and cannot be specified, but it is usually carried out at a temperature of 10 to 150°C above the above-mentioned molding temperature until the desired expansion ratio is achieved.

〔Example〕

The present invention will be further explained with reference to Examples below.

Experimental example 1 Internal volume 4 containing 9 kg of steel balls with a diameter of 12-! Prepare a vibrating mill equipped with four grinding pots. 300 g of magnesium chloride, 60I11 of tetraethoxysilane, and 45 ml of α,α,α-trichlorotoluene were placed in each bottle under a nitrogen atmosphere, and the mixture was ground for 40 hours.

300 g of the thus obtained co-pulverized product was placed in a 51 flask, and 1.5 e of titanium tetrachloride and 1.5 ffi of toluene were added.
was added, stirred at 100°C for 30 minutes, and then the supernatant was removed. 1.5 i of titanium tetrachloride and 1.5 l of toluene were added again, stirred at 100° C. for 30 minutes, and then the supernatant was removed. Thereafter, the solid content was repeatedly washed with n-hexane to obtain a transition metal catalyst slurry. When we sampled a portion and analyzed the titanium content, the titanium content was 1.
It was 9wL%.

In a pressure-resistant glass autoclave with an internal volume of 200 m, 40 d of toluene, 50 q of the above transition metal catalyst, O, 128 aN of diethylaluminium chloride, 0.06 af of ρ-methyl toluate, and 0.20 of triethyl aluminum were placed in a nitrogen atmosphere, and then 4. After pressurizing Og, propylene was charged at a rate of 5 kg/i knee, and polymerization was carried out at 70°C for 2 hours at a constant pressure. After that, the slurry was taken out, filtered and dried to obtain 43g of powder (2), and the limiting viscosity (hereinafter abbreviated as η) was measured with a tetralin solution at 135°C using a differential thermal analyzer.
When the melting point and crystallization temperature were measured with the maximum peak temperature by increasing or decreasing the temperature at 156°C/-10°C, the obtained powder had an η of 1.61, a melting point of 156°C, and a crystallization temperature of 156°C. It was crystalline polypropylene with a temperature of 118°C.

According to elemental analysis, it contained 1.8 wL% of vinylsilane units.

A phenolic stabilizer 10/xo was added to the obtained copolymer.
ooo superposition ratio (to polypropylene copolymer) and calcium stearate 15/10000 weight Jlt ratio, abdicarbonamide 1000/1ooooli I
The ratio was added to make a sheet with a thickness of 2 mm and a thickness of 1 mm. An electron beam (750kV) is applied to this sheet.
ad irradiation, and then the notebook was heated to 250° C. for 10 minutes to obtain a foam sort with a foaming ratio r) 20 (n. The surface of the sheet was smooth, and observation of the cross section showed that it was foamed uniformly.

Comparative Example 1 The η of polypropylene obtained by polymerization without the presence of vinyl silane was 1.61, and when the same procedure was performed using crystalline polyp I-1 pyrene with a melting point of 156°C and a crystallization temperature of 118°C, crosslinking was observed. When the material was heated after being irradiated with radiation, it became deformed.

Example 2 Polypropylene of Allyl 9576 Co., Ltd., 1.3 wtχ was obtained by polymerization using allylsilane instead of vinylsilane, and a foam was produced in the same manner as in Example 1. A uniform foam with an expansion ratio of about 20 times was obtained. Ta.

, Example 3 Example 1 except that azodicarbonamide 2000/10000 weight ratio was added and the electron beam irradiation was set to 2 Mrad.
In the same manner as above, a uniform foam with a foaming ratio of about 30 times was obtained.

Example 4 A uniform foam with a foaming ratio of about 25 times was obtained in the same manner as in Example 1 except that 2 Mrad of r-rays and @CO were used instead of electron beams.

[Effects of the Invention] By carrying out the method of the present invention, a uniform foam can be obtained easily and is extremely valuable industrially.

Claims (1)

[Claims] 1. A method for producing a foamed polyolefin, which comprises irradiating a polyolefin molded product containing an alkenylsilane and olefin copolymer and a foaming agent with radiation, and then foaming the product by heating to a temperature higher than the decomposition temperature of the foaming agent.