JPH0774284B2 - Polyolefin resin foam - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyolefin resin foam. More specifically, it has excellent antistatic properties and surface wettability, such as household items such as bath mats, packings,
The present invention relates to a polyolefin-based resin foam that can be suitably used as a material such as a heat insulating material and an automobile interior material.

[Prior Art] Generally, a foam made of a polyolefin-based resin, particularly a polyethylene-based resin or a polypropylene-based resin has a large hydrophobicity, so that static electricity is remarkably generated, dust is attached to the foam, or static electricity is discharged. This causes a problem such as giving a shock to the human body. In addition, due to its poor hydrophobicity due to its large hydrophobicity, when the surface of the foam is coated with an adhesive, printing ink, etc., it is not applied uniformly, causing a so-called cissing phenomenon. There is a problem that the adhesive strength of the adhesive is small.

Therefore, conventionally, in order to impart antistatic properties to the foam, a method of adding an anionic, cationic or amphoteric surfactant, or a resin described in JP-A-62-121717 in advance to a polyolefin resin. The method of adding a resin described in Japanese Patent Publication No. 1-29820 is adopted.

However, in the method of adding the surfactant, since the surfactant has a relatively small molecular weight of at most about 500 to 600, it is volatilized during the production of the foam or after being made into the foam. Has a problem that it bleeds out over time, contaminates the surface of the foam, causes blocking, and deteriorates adhesiveness, printability, vapor deposition, and the like. Further, in the method of adding the specific resin, since the resin is not a polyolefin-based resin, the buffering property of the polyolefin-based resin foam when formed into a foam is reduced, and further, such a resin is a polyolefin resin. Due to poor compatibility with the system resin, there are problems that voids occur when forming a foam, the expansion ratio decreases due to the escape of foaming gas, and the moldability after forming a foam is poor. is there.

On the other hand, as a method for improving the surface wettability of the polyolefin resin foam, generally, a method of subjecting a corona discharge treatment, a copolymer of ethylene and a vinyl monomer having a specific functional group, or a grafted copolymer is used. The method used is adopted.

However, in the method of performing the corona discharge treatment, there is a problem in terms of so-called durability, which shows a change with time after the treatment. Further, in the method using the copolymer, it is necessary to add a large amount of the copolymer in order to make the surface wettability (surface wetting tension) of the foam practically 37 dyne / cm or more, and therefore the cost is high. In addition, there is a problem that the heat resistance is lowered due to the low melting point of the copolymer.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned prior art,
It is an object of the present invention to provide a polyolefin resin foam which is excellent not only in antistatic property and surface wettability but also in which bleeding and blocking are not generated and which is excellent in printability.

[Means for Solving the Problems] The present invention provides the ethylene structural unit represented by the formula: CH ₂ —CH ₂ in an amount of 65 to 99 mol%, a general formula: (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), an acrylate structural unit of 0 to 15 mol% and a general formula: (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴
Are each an alkyl group having 1 to 4 carbon atoms, R ⁵ is 1 to 4 carbon atoms
An acrylamide structure represented by a 12 alkyl group, an arylalkyl group having 1 to 12 carbon atoms or an alicyclic alkyl group having 1 to 12 carbon atoms, X is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO ₃ ) The present invention relates to a polyolefin resin foam containing a polyolefin resin having a weight average molecular weight of 1000 to 50000, which is linearly and irregularly arranged and has a unit of 1 to 35 mol%.

Polyolefin resin foam of the action and Examples] The present invention, as described above, wherein: the ethylene structural unit 65 represented by CH ₂ -CH ₂
~ 99 mol%, general formula: (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), an acrylate structural unit of 0 to 15 mol% and a general formula: (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴
Are each an alkyl group having 1 to 4 carbon atoms, R ⁵ is 1 to 4 carbon atoms
12 alkyl group, C 1-12 arylalkyl group or C 1-12 alicyclic alkyl group, X is a halogen atom,
CH ₃ OSO ₃ or C ₂ H ₅ OSO ₃ ), and containing a polyolefin resin having a weight average molecular weight of 1000 to 50,000 linearly and irregularly arranged and composed of 1 to 35 mol% of an acrylamide structural unit. is there.

The ratio of ethylene structural units represented by the formula: CH ₂ —CH ₂ in the polyolefin resin is 65
~ 99 mol%. When the proportion of the ethylene structural unit is less than 65 mol%, the softening point of the polyolefin-based resin becomes low to cause tack and stickiness, and when it exceeds 99 mol%, the polyolefin-based resin is The antistatic property of becomes too small. In the present invention, the proportion of the ethylene structural unit is particularly preferably 85 to 97 mol% from the viewpoint of the balance between the softening point and the antistatic property.

The general formula in the polyolefin resin: The ratio of the acrylate structural unit represented by the formula (wherein R ¹ is the same as above) is 0 to 15 mol%. When the proportion of the acrylate structural unit exceeds 15 mol%, the softening point of the polyolefin resin becomes low and tack or stickiness occurs. In the present invention, the presence of the acrylate structural unit is preferable because it imparts toughness and impact resistance. In the present invention, the proportion of the acrylate structural unit is particularly preferably 1 to 15 mol%, especially 3 to 7 mol% from the viewpoint of the balance between the softening point and the toughness and impact resistance.

In the acrylate structural unit, R ¹ has 1 to 4 carbon atoms.
Is an alkyl group. Specific examples of R ¹ include methyl group, ethyl group, n-propyl group, i-propyl group, n
-Butyl group and i-butyl group are mentioned, and these groups are 1
It may be mixed in the molecule. Among these groups, the methyl group and the ethyl group are preferable for maintaining the softening point of the polyolefin resin.

The general formula in the polyolefin resin: The ratio of the acrylamide structural unit represented by the formula (wherein R ² , R ³ , R ⁴ and R ⁵ are the same as above) is 1 to 35 mol%. When the proportion of the acrylamide structural unit is less than 1 mol%, the antistatic property becomes too small, and
If it exceeds mol%, the polyolefin resin becomes hygroscopic. In the present invention, the proportion of the acrylamide structural unit is particularly preferably 3 to 15 mol% in terms of antistatic property and hygroscopic property.

In the acrylamide structural unit, R ² has 2 to 2 carbon atoms.
8 is an alkylene group. Specific examples of R ² include:
Examples thereof include ethylene group, propylene group, hexamethylene group, neopentylene group, and the like.
It may be mixed in the molecule. Among these groups, an ethylene group and a propylene group are preferable, and a propylene group is particularly preferable, from the viewpoint of ease of production and economy.

R ³ and R ⁴ are each an alkyl group having 1 to 4 carbon atoms. Specific examples of R ³ and R ⁴ include a methyl group,
Examples thereof include an ethyl group, a propyl group, and a butyl group, and these groups may be mixed in one molecule. Among these groups, a methyl group and an ethyl group are preferable from the viewpoint of antistatic property.

R ⁵ is an alkyl group having 1 to 12 carbon atoms, an arylalkyl group having 1 to 12 carbon atoms, or an alicyclic alkyl group having 1 to 12 carbon atoms. Specific examples of R ⁵ include, for example, methyl group, ethyl group, n-propyl group, i-propyl group and n-propyl group.
Butyl group, sec-butyl group, n-octyl group, n-lauryl group and other alkyl groups; benzyl group, 4-methylbenzyl group and other arylalkyl groups; cyclohexyl group,
Examples thereof include alicyclic alkyl groups such as a methylcyclohexyl group, and these groups may be mixed in one molecule. Note that R ⁵ is preferably a linear alkyl group or an arylalkyl group from the viewpoint of heat resistance, and is preferably a lower alkyl group from the viewpoint of antistatic properties. Especially preferred
Examples of R ⁵ include a methyl group and an ethyl group.

The X is, for example, a halogen atom such as Cl, Br or I, CH
₃ OSO ₃ or C ₂ H ₅ OSO ₃ , which may be mixed in one molecule. Among these, Cl, CH ₃ OSO ₃ and C ₂ H ₅ OSO ₃ are preferable from the viewpoint of antistatic property.

The weight average molecular weight of the polyolefin resin is 1000 to
It is 50,000. When the weight average molecular weight is less than 1000, the molecular weight becomes too small to volatilize when heated, and when it exceeds 50,000, the viscosity when melted becomes too large, resulting in poor workability. Become. The preferred weight average molecular weight is 3000 to 30,000.

The weight average molecular weight in the present invention refers to a monodisperse polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography (GPC).

Since the polyolefin resin used in the present invention is hardly soluble in a normal gel permeation eluent such as tetrahydrofuran (THF) or xylene, its weight average molecular weight cannot be easily measured. , Polymers, Vol.44, No.2, pp.139-141 (1987)
Year)).

Formula that is an intermediate of the above-mentioned polyolefin resin: CH ₂ -C
An ethylene structural unit represented by H ₂ , a general formula: (Wherein R ¹ is the same as above) and a general formula: (In the formula, R ² , R ³ and R ⁴ are the same as described above) The olefinic copolymer having a weight average molecular weight of 1000 to 50000 linearly and irregularly arranged consisting of an acrylamide structural unit is, for example, Obtained by the method.

First, the raw material of the olefin-based copolymer is not particularly limited, but more advantageously ethylene (C ₂ H ₄ ) and the general formula: CH ₂ CHCOOR ¹ (wherein R ¹ is the same as above). A (partial) hydrolyzate of a copolymer with the acrylate represented is used. Such a copolymer can be easily obtained by copolymerizing ethylene and the acrylate by a high pressure polymerization method.

The ratio of the ethylene structural unit derived from ethylene to the acrylate structural unit derived from the acrylate determines the ratio of the ethylene structural unit, the acrylate structural unit and the acrylamide structural unit of the obtained olefinic copolymer.

Since the copolymer usually has a high molecular weight of about 5 to 300 as a melt index, it is reduced in molecular weight by, for example, a degradation method in which hydrolysis and thermal decomposition are simultaneously performed under high temperature and high pressure in the presence of water. It is preferable.

At this time, the general formula derived from acrylate: (In the formula, R ¹ is the same as above), all or part of the acrylate structural unit is hydrolyzed to form the formula: It becomes an acrylic acid structural unit represented by.

To reduce the molecular weight by thermally decomposing the copolymer, to prepare a copolymer having a weight average molecular weight of 1000 to 50,000, the copolymer is reacted in the presence of water at a reaction temperature of 150 to 500.
The molecule may be cleaved by heating at a temperature of 3 to 500 kg / cm ² .

Further, in the present invention, the ratio of the acrylic acid structural unit can be appropriately adjusted by adjusting the charged amount of water, the reaction temperature, the pressure and the reaction time.

A specific example of the degradation method is disclosed in Japanese Patent Laid-Open No. 53-57.
295, JP-A-53-65389, JP-A-60-78008
The methods described in JP-A No. 60-79015 and the like.

Since the polyolefin resin used in the present invention may impair the commercial value when it is colored, the raw material used in the present invention is, for example, JP-A-60-
It is preferable to use the product of the method exemplified in 79008.

The polyolefin resin used in the present invention can be obtained by using the thus obtained intermediate of the polyolefin resin.

The method for producing the polyolefin resin used in the present invention from the intermediate is not particularly limited. An example thereof will be described below.

Examples of the intermediate include benzene, toluene, xylene,
It is dissolved in an inert solvent such as an aromatic or aliphatic hydrocarbon such as cyclohexanone, decane, cumene or cymene, and 100 to 150 mol% of a dialkylamine such as a dialkylaminoalkylamine with respect to the carboxyl group of the intermediate. After adding a system monomer and reacting at 130 to 220 ° C. to convert the carboxyl group contained in the acrylic acid structural unit into a dialkylaminoalkylamide group to form an intermediate, for example, an alkyl halide, a dialkyl nitrate, etc. The linear random copolymer of the present invention can be obtained by cation-modifying with a quaternizing agent.

The polyolefin resin thus obtained has excellent charging.
Exhibits preventive properties. The reason why the antistatic property is exhibited is
Although it is not certain, the accompaniment contained in polyolefin resin
Lilamide structural unit takes in the water contained in the air
See, x Is ionized and exhibits electrical conductivity,
It is considered that this is due to the fact that it exhibits a low electric resistance.

Further, in the present invention, the acrylamide structural unit does not exhibit volatility even at high temperatures, and since it is chemically incorporated into the polyolefin resin used in the present invention, there is no volatilization during processing, It is considered that blocking does not occur after processing.

The polyolefin resin foam of the present invention contains the above polyolefin resin, and the above polyolefin resin may be used alone or in combination with other polyolefin resins.

Examples of the other polyolefin resins include ethylene-propylene copolymers having an ethylene content of 2 to 30% by weight, butene-propylene copolymers containing butene-
Terpolymer further copolymerized with 1, high-pressure low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, the above-mentioned ethylene-vinyl acetate Saponified copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, ethylene- (meth) acrylic acid-maleic anhydride terpolymer,
Examples thereof include ethylene- (meth) acrylic acid ester-maleic anhydride terpolymer, and these resins may be used alone or in combination of two or more.

When the polyolefin resin and the other polyolefin resin are used in combination, the amount of the polyolefin resin used is 100 parts by weight of the resin component contained in the obtained polyolefin resin foam (the same applies hereinafter. )
On the other hand, 0.1 part or more, preferably 20 parts or more is desirable in order to impart antistatic property and surface wettability to the obtained polyolefin resin foam.

In the present invention, as long as the object of the present invention is not hindered, for example, calcium carbonate, talc, inorganic filler such as glass single fiber, antioxidant, flame retardant, colorant,
Various auxiliaries such as polyfunctional monomers may be contained in the polyolefin resin foam of the present invention.

Further, in the present invention, a known low molecular weight surfactant may be used within a range not exceeding 30 parts with respect to 100 parts of the polyolefin resin. When the surfactant is used within the range of not more than 30 parts, no bleeding from the obtained foam is observed.

The method for producing the polyolefin resin foam of the present invention is not particularly limited, and known production methods can be applied. Specific examples thereof include, for example, a method of mixing a decomposable foaming agent with a foamable resin composition containing the polyolefin resin, introducing the mixture into an extruder, and decomposing the foaming agent to foam, and the foamable resin composition. Is introduced into an extruder, and a so-called extrusion foaming method in which an evaporative solvent is pressed into the extruder for foaming, a foamable resin composition is filled into a mold together with a mixture of a decomposable foaming agent and a peroxide compound and pressurized. By heating, decomposing the peroxide compound to crosslink, further decomposing the decomposition type foaming agent and releasing the pressure at the same time to form a foam, the so-called block foaming method, introducing the foamable resin composition into the extruder, and forming it into a sheet. After molding,
Examples include a method of irradiating with an electron beam or adding a peroxide compound to crosslink and heat foam.

The foam of the present invention thus obtained, further subjected to corona discharge treatment on at least one side to increase the surface wetting tension,
The adhesiveness with various water-soluble coating agents can be improved. In addition, by providing a coating agent layer, various skin materials, films, sheets, other foams, metal foil, paper,
A nonwoven fabric made of natural fibers or synthetic fibers or synthetic leather is laminated to form a composite, which can be molded by various methods.

Next, the polyolefin resin foam of the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1 Formula: CH ₂ -CH ₂ ethylene structural units 85 mole% represented by the formula: An acrylate structural unit represented by 5 mol% and a formula: Polyolefin resin having a weight average molecular weight of 29000, which is linearly irregularly arranged and consists of 10 mol% of acrylamide structural unit represented by, is pulverized into 32 mesh pass 30 parts and high pressure method low density polyethylene (density: 0.921 g / cm
³ , melt index: 3.7 g / 10 minutes, particle diameter: 32 mesh pass) 10 parts of azodicarbonamide as a foaming agent is added to 100 parts of a mixed resin and mixed to form a foamable resin composition. I got it.

The foamable resin composition obtained below was introduced into an extruder heated to 120 to 130 ° C., melted and kneaded to have a thickness of 1.5 m.
It was formed into a molten continuous sheet having an m and a width of 500 mm. This sheet was irradiated with an electron beam of 5 Mrad by an electron beam irradiator to be crosslinked to obtain a crosslinked foamable sheet.

The obtained crosslinked foamable sheet was continuously introduced into a vertical hot air foaming machine in a heating atmosphere of 230 ° C. to obtain a foam. This foam had an overall thickness of 3.1 mm, an overall width of 1170 mm, and an apparent expansion ratio of 20 times.

When the surface resistivity of the obtained foam was examined according to the following method, it was found to be extremely small at 1.6 × 10 ⁹ Ω and that it had excellent antistatic properties.

Next, after leaving the obtained foam in an atmosphere of 40 ° C. and 80% RH (relative humidity) for 7 days, the surface of the foam was observed. I printed with polypropylene printing ink on the surface,
There were no print defects due to bleed-out.

Next, one side of the obtained foam was subjected to corona discharge treatment, and the surface wetting tension was set to 45 dyne / cm or more, and the adhesion with various coating agents could be improved.

In addition, after providing a coating agent layer and laminating various skin materials, films, sheets, other foams, metal foils, papers, non-woven fabrics made of natural fibers or alloy fibers or synthetic leathers to form a composite, various methods are used. Then, it could be molded into a desired shape.

(Surface specific resistance) The foam is cut out into 10 cm x 10 cm, and left in a constant temperature and constant temperature room controlled at 20 ° C and 60% RH for 48 hours for aging.

After the aging, the surface resistivity is measured in the atmosphere.

Measuring instrument: Super Insulator (VE-40 manufactured by Kawaguchi Electric Co., Ltd.)
Room temperature measurement box (RC-02 type) is connected to the model) Measurement conditions: Applied voltage 100V The value measured with this unit is used.

The surface resistivity of 1 × 10 ¹³ Ω or less and the half-life of the charge of 3 minutes or less are considered to have antistatic properties.

Example 2 Instead of the high-pressure low-density polyethylene used in Example 1, linear low-density polyethylene (density: 0.930 g / cm ³ , melt index: 3.7 g / 10 minutes, particle size: 32 mesh pass) was used. A foam was obtained in the same manner as in Example 1 except that the amount of the polyolefin resin used was changed from 30 parts to 20 parts and the amount of the azodicarbonamide used was changed from 10 parts to 6 parts. The resulting foam has an overall thickness of 3.2 mm and an overall width of 117
It was 0 mm and the apparent expansion ratio was 20 times.

When the surface wetting tension of the obtained foam was examined according to JIS-K 6768, it was 39 dyne / cm, and the surface wetting tension of the foam consisting of linear low-density polyethylene was 31 dyne / c.
It showed very good surface wettability compared with m. Further, when the surface resistivity was examined in the same manner as in Example 1,
It was extremely small, 2.3 × 10 ¹¹ Ω.

Next, when a printing ink or an adhesive was applied on the surface of the obtained foam, no cissing phenomenon was observed and the adhesiveness with these was excellent.

Furthermore, when metal vapor deposition was performed on the surface of the obtained foam, a very strong adhesive force was obtained.

From the above, it can be seen that the foamed product of the present invention has not only improved adhesiveness due to improved surface wettability, but also excellent adhesiveness with the metal film.

Example 3 In Example 1, instead of the polyolefin resin and the linear low-density polyethylene, 85 mol% of an ethylene structural unit represented by the formula: CH ₂ —CH ₂ , the formula: An acrylate structural unit represented by 5 mol% and a formula: 50 parts of a polyolefin resin having a weight-average molecular weight of 33000 linearly and irregularly arranged of 10 mol% of acrylamide structural unit represented by and 50 parts of low-density polyethylene are melted by an extruder heated to 110 to 120 ° C. The volatile solvent is blown from the middle of the barrel of the extruder under pressure, kneaded until the foaming agent is evenly dispersed in the resin, and the temperature is adjusted so that the viscosity is suitable for foaming. The foam was obtained by extruding and expanding under atmospheric pressure. This foam had an overall thickness of 10 mm, an overall width of 600 mm, and an apparent expansion ratio of 15 times.

Next, as the physical properties of the obtained foam, the surface resistivity was examined in the same manner as in Example 1, and the half-life of charge, bleed-out and blocking shear force were examined according to the following methods. The results are shown in Table 1.

(Half-life of charge) A static Honest meter (manufactured by Shishido Shokai Co., Ltd.) was used as a sample in the same atmosphere as when the surface resistivity was measured.
Apply a voltage of 10KV and obtain the decay rate of the applied charge as the half-life.

(Bleed out) After overlaying the additive-free biaxially oriented polypropylene film on the surface of the foam and putting it in an atmosphere of 40 ° C, 80% RH for 7 days,
The film is taken out, the film is peeled off from the foam, and the presence or absence of deposits on the surface of the film is examined.

(Blocking shearing force) Two foams are overlapped over a width of 3 cm and a length of 4 cm,
A weight of 550 g is placed on this and put in an atmosphere of 40 ° C. and 80% RH for 7 days, and then the shear peeling force of the two foams is determined by a Shopper type tensile tester.

A shear peel force of 1000 g or less is regarded as acceptable. The amount is preferably 500 g or less.

Example 4 Formula: 80 mol% of ethylene structural unit represented by CH ₂ —CH ₂ and formula: 20 parts of a linearly irregularly arranged polyolefin resin having a weight average molecular weight of 35,000 and having a weight average molecular weight of 35,000 and pulverized into a 32 mesh path and 8 parts of azodicarbonamide as a foaming agent Linear low-density polyethylene (density: 0.921 g / cm ³ , melt index: 3.2 g / 10 minutes, particle size: 32 mesh pass) 8
0 parts were added and mixed to obtain a foamable resin composition.

A crosslinkable foamable sheet was produced in the same manner as in Example 1 by using the foamable resin composition obtained next, and then heated to obtain a foam. This foam had an overall thickness of 2.5 mm, an overall width of 1000 mm, and an apparent expansion ratio of 25 times.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 1.

Example 5 In Example 4, as the polyolefin resin, the formula:
80 mol% of an ethylene structural unit represented by CH ₂ -CH ₂ ,
formula: An acrylate structural unit represented by 1 mol% and a formula: Was used. 20 parts of a polyolefin resin having a weight average molecular weight of 33000 linearly and irregularly arranged with 19 mol% of acrylamide structural unit represented by and 80 parts of the same linear low-density polyethylene as used in Example 4 were used. Otherwise, Example 4
A foam was obtained in the same manner as in. This foam had an overall thickness of 3.9 mm, an overall width of 1500 mm, and an apparent expansion ratio of 40 times.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 1.

Example 6 Formula: Ethylene structural unit represented by CH ₂ —CH ₂ 88 mol%, Formula: An acrylate structural unit represented by 3 mol% and a formula: The linearly irregularly arranged polyolefin resin having a weight average molecular weight of 34400 consisting of 9 mol% of acrylamide structural unit represented by is crushed to have a 32 mesh path, and 10 parts of polypropylene (melt index: 2.5 g /
10 minutes, particle size: 32 mesh pass) 90 parts were added and mixed to obtain a foamable composition.

Next, a foam was obtained in the same manner as in Example 3 using the obtained foamable composition. The resulting foam has an overall thickness
It had a width of 2.5 mm, an overall width of 450 mm, and an apparent expansion ratio of 9 times.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 1.

Comparative Example 1 A foamable composition was obtained by mixing 99 parts of polypropylene (melt index: 2.5 g / 10 minutes, particle size: 32 mesh pass) and 1 part of stearic acid monoglyceride as an antistatic agent.

Next, a foam was obtained in the same manner as in Example 3 using the obtained foamable composition.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 2.

Comparative Example 2 99.2 parts of polypropylene (melt index: 2.5 g / 10 minutes, particles: 32 mesh pass) and the formula as an antistatic agent: A betaine-type amphoteric surfactant of 0.8 part was mixed to obtain a foamable composition.

Next, a foam was obtained in the same manner as in Example 3 using the obtained foamable composition.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 2.

Comparative Example 3 Linear low-density polyethylene (density: 0.921 g / cm ³ , melt index: 3.2 g / 10 minutes, particle size: 32 mesh pass) 98.
5 parts, stearic acid monoglyceride as antistatic agent and formula: A betaine-type amphoteric surfactant represented by the following formula (1.5 parts) was mixed at a weight ratio of 1: 1 and 10 parts of azodicarbonamide as a foaming agent were mixed to obtain a foamable composition.

A foam was obtained in the same manner as in Example 4 using the foamable composition obtained below.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 2.

Comparative Example 4 95 parts of ethylene-propylene copolymer having an ethylene content of 5% by weight (melt index: 1.2 g / 10 minutes, particle size: 32 mesh pass), and sodium dodecylbenzenesulfonate as an antistatic agent and polyethylene glycol 1: 5 parts mixed in a weight ratio of 1, azodicarbonamide as a foaming agent
A foamable composition was obtained by mixing 10 parts and 2 parts of dicumyl peroxide as a crosslinking agent. The foamable composition thus obtained was melted and kneaded with an extruder heated to 160 to 170 ° C., and a predetermined amount of the composition was put into a heated mold and hermetically sealed.
Further, in this state, the foaming agent was decomposed by heating to a temperature at which the foaming agent decomposes, and then pressure was released to obtain a foam.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 2.

Comparative Example 5 A foamable composition was obtained by mixing 99.2 parts of polypropylene (melt index: 2.5 g / 10 minutes, particle size: 32 mesh pass) and 1 part of stearyldiethanolamine as an antistatic agent.

Next, a foam was obtained in the same manner as in Example 3 using the obtained foamable composition.

The physical properties of the obtained foam were examined in the same manner as in Example 3.
The results are shown in Table 2.

From the results shown in Table 1, the polyolefin resin foam of the present invention has a surface resistivity of 1 ×, which is an index of antistatic property.
It can be seen that the foam has an excellent antistatic property of 10 ¹³ Ω or less and a charge half-life of 180 seconds or less, and has no bleed-out of the antistatic component from the foam, and thus is excellent in antistatic property without blocking.

On the other hand, the foams obtained in Comparative Examples 1 to 5 are those in which the conventional comparatively low molecular weight surfactant type antistatic agent is used, and the results shown in Table 2 show that the antistatic property is If the content is to be satisfied, the antistatic agent bleeds out from the foam, and it is found that blocking occurs.

From the above, the polyolefin-based resin foam of the present invention has excellent antistatic properties, and further, since there is no bleed-out of the antistatic agent and blocking does not occur, for example, it is necessary to prevent the occurrence of damage due to static electricity. It can be seen that it can be preferably used for.

Examples 7 to 10 Foams were obtained in the same manner as in Examples 3 to 6 except that the mixing ratio of the polyolefin resin and the other polyolefin resin was changed as shown in Table 3. Using the obtained foam, the surface specific resistance was examined in the same manner as in Example 1 and the surface wetting tension, cissing and printability were examined according to the following methods. The results are shown in Table 3.

(Surface wetting tension) Measure according to JIS-K 6768.

(Hajiki) Printing ink for cellophane (CCST: Toyo Ink Mfg. Co., Ltd.)
Product) is applied with a # 50 bar coater and left in the room after application to observe the ink application surface, and it is judged whether the ink film on the ink application surface is circular or not. "Good", and "Something that caused a slight loss" is rejected.

(Printability) Printing ink for cellophane (CCST: Toyo Ink Mfg. Co., Ltd.)
Product) is applied with a # 50 bar coater, dried with a hot air dryer at 80 ° C. to remove the solvent, and a cellophane adhesive tape is attached to the ink surface to quickly peel 180 °. The printability is evaluated by the ink and the remaining area of the adhesive tape sticking part.

The evaluation criteria are as follows.

(Evaluation Criteria) Remaining area is less than 50%: Index 1 Remaining area is 50% or more and less than 70%: Index 2 Remaining area is 75% or more and less than 90%: Index 3 Remaining area is 90% or more and less than 100%: Index 4 100% remaining area: Index 5 Comparative Example 6 A foam was obtained in the same manner as in Comparative Example 1 except that the antistatic agent was not used.

The physical properties of the obtained foam were examined in the same manner as in Examples 7-10. The results are shown in Table 4.

Comparative Example 7 In Comparative Example 2, an ethylene-vinyl acetate copolymer (vinyl acetate content: 20% by weight, weight average molecular weight: 56000) was used in place of the antistatic agent, and an ethylene-vinyl acetate copolymer / polypropylene weight ratio was used. A foam was obtained in the same manner as in Comparative Example 2 except that the ratio was adjusted to 15/85.

The physical properties of the obtained foam were examined in the same manner as in Examples 7-10. The results are shown in Table 4.

Comparative Example 8 In Comparative Example 3, instead of the antistatic agent, an ethylene-ethyl acrylate copolymer (ethyl acrylate content: 1
8% by weight, weight average molecular weight: 50,000)
A foam was obtained in the same manner as in Comparative Example 3 except that the weight ratio of ethyl acrylate copolymer / low density polyethylene was adjusted to 10/90.

The physical properties of the obtained foam were examined in the same manner as in Examples 7-10. The results are shown in Table 4.

Comparative Example 9 In Comparative Example 4, an ethylene-ethyl acrylate-maleic anhydride terpolymer was used instead of the antistatic agent (ethyl acrylate content: 14% by weight, maleic anhydride content: 2
Wt%, weight average molecular weight: 58000), except that the ethylene-ethyl acrylate-maleic anhydride terpolymer / ethylene-propylene copolymer was adjusted to a weight ratio of 20/80 and Comparative Example 4 A foam was obtained in the same manner as in.

The physical properties of the obtained foam were examined in the same manner as in Examples 7-10. The results are shown in Table 4.

Comparative Example 10 In Comparative Example 5, an ethylene-methyl methacrylate-maleic anhydride terpolymer was used instead of the antistatic agent (methyl methacrylate content: 13% by weight, maleic anhydride content: 2% by weight, weight average molecular weight: 61000). Was used to prepare a foamed product in the same manner as in Comparative Example 5 except that the ethylene-methyl methacrylate-maleic anhydride terpolymer / polypropylene was adjusted to a weight ratio of 15/85.

The physical properties of the obtained foam were examined in the same manner as in Examples 7-10. The results are shown in Table 4.

As is clear from the results shown in Table 3, Examples 7-10
The obtained polyolefin resin foam of the present invention has a clearly improved surface wettability, prevents cissing of the coating agent without physical surface treatment, and has good printability, adhesiveness and vapor deposition property. Further, it can be seen that the surface resistivity, which is an index of antistatic property, is 1 × 10 ¹³ Ω or less, which is excellent in antistatic property.

On the other hand, the conventional foams obtained in Comparative Examples 6 to 10 are:
As shown in Table 4, unless a corona discharge treatment is applied, unless a coating agent of a specific component is used, cissing occurs, and either printability, adhesiveness, or vapor deposition property is not satisfied. It did not have a good antistatic property.

Thus, the foam having excellent surface wettability of the present invention can be subjected to processing such as printing, vapor deposition, and laminating, but even if it is used alone, there is no obstacle due to static electricity. It can be preferably used in fields such as materials.

[Effects of the Invention] The polyolefin resin foam of the present invention has an excellent antistatic property without bleed-out, and therefore has no dust adhesion and does not give a shock to a human body due to electrostatic discharge. It is a foam with excellent handling properties.

Further, the polyolefin-based resin foam of the present invention is a foam exhibiting extremely excellent surface wettability and having excellent adhesiveness, repellency of a coating, printability and vapor deposition.

Claims (1)

[Claims] 1. An ethylene structural unit represented by the formula: CH ₂ —CH ₂ of 65 to 99 mol%, a general formula: (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), an acrylate structural unit of 0 to 15 mol% and a general formula: (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴
Are each an alkyl group having 1 to 4 carbon atoms, R ⁵ is 1 to 4 carbon atoms
An acrylamide structure represented by a 12 alkyl group, an arylalkyl group having 1 to 12 carbon atoms or an alicyclic alkyl group having 1 to 12 carbon atoms, X represents a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO ₃ ) A polyolefin resin foam comprising a polyolefin resin having a weight average molecular weight of 1000 to 50,000 linearly and irregularly arranged in units of 1 to 35 mol%.