JPH06287340A - Crosslinked polyolefin resin foam - Google Patents

Abstract

PURPOSE:To provide a foam which is excellent in moldability and adhesiveness and gives a resin plate laminate esp. excellent in punchability. CONSTITUTION:A crosslinked polyolefin resin foam contains 25-75wt.% linear low-density polyethylene. 3-18wt.% ethylene-vinyl acetate copolymer, and 15-50wt.% inorg. filler having a specific surface area of 1.5-4m<2>/g.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic filler-containing polyolefin foam, which has particularly good foam moldability, heat resistance, adhesiveness to a resin plate, and punching property of a laminate with a resin plate. It relates to a LLDPE resin crosslinked foam.

[0002]

2. Description of the Related Art Polyolefin foams have excellent mechanical strength, texture and cushioning properties, and are widely used as sound deadening materials, heat insulating materials, sports goods and food packaging materials. Among them, linear polyethylene (commonly known as LLDPE) foam is superior in heat resistance to strain recovery after compression as compared with polystyrene foam, and is heat resistant even in comparison with low density polyethylene (LDPE) foam. Since it is excellent in compressive strength, tensile strength, etc., it is suitable for building materials such as interior materials for automobiles, heat insulating materials requiring heat resistance, cushioning materials, and packing materials. However, since the linear polyethylene resin has poor cross-linking reactivity and retention of decomposition gas of the foaming agent, many large bubbles are generated, and there is a problem that foaming moldability is difficult. As a solution to these problems, a method of adding a surfactant such as a fatty acid ester or a fatty amide is known, but there is a problem that the additives are separated during the production process of the foam and the bubbles cannot be sufficiently controlled. . Further, the foam obtained by the method of adding a polyolefin having a low degree of polymerization disclosed in JP-A-61-83236 has a problem that the adhesiveness is deteriorated due to the bleeding of the additive, and thus a vinyl chloride board, an acrylic board or the like is synthesized. There were serious defects in various applications where the resin plate was used in combination. Further, the linear polyethylene foam has a lack of machinability, and when the above laminated product is punched out and used, there is a problem that the cut surface is crispy and the appearance is significantly impaired.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a foam which is particularly excellent in moldability, adhesiveness and punchability of a laminate with a resin plate.

[0004]

The present invention is directed to the cross-linking foaming of linear low-density polyethylene by using a vinyl acetate copolymer in combination with an inorganic filler having a specific surface area. It was made based on the finding that the foams proceed uniformly and a foam having excellent characteristics can be obtained. That is, in the present invention, (A) linear low-density polyethylene 25 to 75% by weight, (B) ethylene vinyl acetate copolymer 3 to 18% by weight, and (C) specific surface area are
Provided is a polyolefin resin crosslinked foam comprising 15 to 60% by weight of an inorganic filler of 1.5 to ⁴ m ² / g.

Linear low density polyethylene of component A of the present invention
Is what is usually called LLDPE.
Copolymer of α-olefin with 3 to 8 carbon atoms (α-
Olefin composition 0.7 to 10 mol%), usually branched carbon
A polyethylene having a linear skeleton with a prime number of 8 or less
It Examples of the α-olefin include propylene and butene.
-1, pentene-1, hexene-1, heptene-1, o
Examples include cutene-1, 4-methylpentene-1 and the like.
Especially preferred are propylene and butene-1. Above linear low density
Polyethylene has a density of 0.915 to 0.945 g / cm³Nomono
Is preferred. Density is 0.915g / cm³Less than is a tree
Punching of laminated product with synthetic resin plate due to lack of rigidity of fat
Sometimes the foam will deform too much and the resin plate will crack easily.
45 g / cm ³If the value exceeds the range, the compression strain recovery of the foam will be
Because it will decrease. More preferably 0.920 g / cm³
~ 0.940 g / cm³Is. Also, melt flow rate
(2.16Kg load, 190 ℃) 0.2 ~ 5g / 10min
Is preferred. Melt flow rate less than 0.2 g / 10 minutes
The product with high viscosity when melted is difficult to obtain with high expansion ratio.
Peg. Also, if it exceeds 5 g / 10 minutes, the fluidity is large.
This is because it becomes too tight and the bubble diameter tends to be non-uniform.
More preferably, it is 1 to 3 g / 10 minutes. In foam
The linear low density content is 25 to 75% by weight. Tsuma
If the content is less than 25% by weight, the heat resistance is not sufficient and the sign material
When used as, it tends to warp, and it is 75% by weight.
If it exceeds the limit, the cut surface will be scratched during punching.
Because. More preferably, it is 50 to 60% by weight.
It The straight chain low density polyethylene of the component A of the present invention is
Easy to enter as Kasen-L (Sumitomo Chemical Co., Ltd.)
You can get it.

As the ethylene-vinyl acetate copolymer of the component B of the present invention, any vinyl acetate content can be used, but the vinyl acetate content is 2 to 15% by weight.
(Hereinafter abbreviated as “%”) is preferable. Vinyl acetate content 2
If it is less than 15%, the compression strain recovery property and adhesiveness of the foam will be poor, and if it exceeds 15%, the heat resistance and punching property will be poor. More preferably, it is 3 to 10%. Further, those having a melt flow rate of 0.5 to 10 g / 10 minutes are preferable. If the melt flow rate is less than 0.5 g / 10 minutes, the viscosity at the time of melting is high and unevenness tends to occur during kneading.
If it exceeds g / 10 minutes, the fluidity becomes too large,
This is because the bubble diameter tends to be non-uniform. Furthermore, it is preferably 1 to 3 g / 10 minutes. The content of component B is 3 to 1
8% by weight. This is because if the content is less than 3% by weight, the adhesiveness is poor and the compression strain recovery property is poor, and if it exceeds 18% by weight, the heat resistance decreases. More preferably, 5 to 15
% By weight. The ethylene-vinyl acetate copolymer of the component B of the present invention can be easily obtained as Evatate (Sumitomo Chemical Co., Ltd.).

The inorganic filler of the component C of the present invention has a specific surface area of 1.
Fine particles of 5 to ⁴ m ² / g. If the specific surface area exceeds 4 m ² / g, poor dispersion due to aggregation easily occurs, and if it is less than 1.5 m ² / g, large holes are likely to occur in the foam due to gas escape. More preferably, it is 2 to 3 m ² / g. The specific surface area of the inorganic filler can be easily measured by, for example, the air permeation method. The content of component C is 15 to 60% by weight
Is. This is because if it is less than 15% by weight, heat resistance, foam moldability and adhesiveness are poor, and if it exceeds 60% by weight, foam moldability and compressive strain recovery are poor. More preferably, 30 to 5
It is 0% by weight. As the fine particle inorganic filler of C component,
Calcium carbonate, talc, clay, silica, aluminum hydroxide, magnesium hydroxide, zeolite, etc. are used.
More preferably, ground calcium carbonate having a specific surface area of 2 to 3 m ² / g is preferable. Further, those having an average particle size of 0.5 to 0.9 μ are preferable.

In the present invention, it is particularly preferred that the component A, the component B and the component C in the foam composition are contained within the range represented by the following formula. . 0.6 <(C × s) / (A + B × 3) <2.6 (wherein A, B and C are% by weight in the foam of components A, B and C, s is the specific surface area of component C) (M ² / g).) In particular,
This is because when the content is within this range, the foamed product has good foamability, little variation in cell diameter, and excellent compression strain recovery and punching properties. In the present invention, the above-mentioned components A to C are essential, and a foaming agent and a cross-linking agent which are usually used for them are further added, and if necessary, a high-density polyethylene and a high-pressure method are used within a range not impairing the object of the present invention. Polyolefin such as density polyethylene, polypropylene polybutadiene, foaming aid,
The foam of the present invention can be produced by combining a crosslinking aid, a lubricant, an antioxidant, an ultraviolet absorber, an antistatic agent, a flame retardant, a colorant and the like and crosslinking and foaming them by a conventional method. As the foaming agent, for example, one or two of pyrolyzable foaming agents such as azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, P, P'-oxybisbenzenesulfonylhydrazide, etc. should be used. You can The amount used is, for example, 1 to 10% by weight based on 100% by weight of the foam raw material. As the cross-linking agent, one or two kinds of organic peroxides such as dicumyl peroxide and ditertiary butyl peroxide can be used. Used in 100% by weight of foam material
An example is 0.3 to 3% by weight.

For example, the foam of the present invention can be manufactured as follows. First, the components A, B and C are mixed with a thermal decomposition type foaming agent and a cross-linking agent, and if necessary various additives, preferably evenly or without mixing, an internal mixer, a Banbury mixer, The mixture is uniformly melted and kneaded by a device such as a pressure kneader, and then formed into a desired shape such as a sheet by a device such as a roll and an extruder. Then, for example, it is preferable to perform the melt-kneading step at a temperature of 90 to 140 ° C. and the forming step such as sheeting at a temperature of 80 to 130 ° C. Moreover, this condition is a temperature condition in which the foaming agent and the cross-linking agent are substantially non-decomposing. For example, in the case of one-step pressing and heat foaming, it is preferable to form a sheet having a thickness of 0.5 to 3.0 mm. Next, the mixed composition prepared in the above step is subjected to cross-linking foaming at a temperature of 150 to 190 ° C. and a pressure of 150 to 200 kg / cm ² by a one-step processing using a pressure press device or the like and a heat foaming method. By this one-step pressurization and heat foaming, the components A and B are foamed and crosslinked to obtain the foamed product of the present invention. Thus, the open cell rate is 60 to 100% and the bulk density is 0.03 to 0.3 g /
A cm ³ foam can be obtained. Although the thickness is arbitrary, a thickness of 20 to 60 mm is usually obtained.

[0010]

According to the present invention, there are few large bubbles,
It is a foam with small and uniform cells, heat resistance,
It is possible to provide an LLDPE-based resin crosslinked foam having excellent adhesiveness with a resin plate and punching properties of a laminate with a resin plate. Therefore, the foam of the present invention can be used as a signboard material as well as a heat insulating material, a cushioning material, a packaging material, which requires heat resistance,
It is suitable for use as automobile members, and particularly suitable for various purposes such as laminating with a synthetic resin plate and punching. Next, the present invention will be described with reference to examples.

[0011]

【Example】

Example 1 After uniformly mixing the components described in Tables 1 to 4, these were melted and kneaded by an internal mixer, and then formed into a sheet by two rolls, and a single-stage pressurization at a foaming temperature of 175 ° C., a heating foaming method. Thus, foams having a composition shown in Tables 1 to 4 (foaming ratio: about 10 times, thickness: 40 mm) were obtained. The heat resistance, foam forming property, compression strain recovery property, adhesive property and punching property of the foam thus obtained were evaluated as follows. The results are summarized in Tables 1 to 4. The heat resistant foam is cut into 100 mm × 100 mm × 10 mm pieces and placed in a hot air oven at 80 ° C. and heated for 2 hours. After cooling for 2 hours, the dimensions are measured and the rate of dimensional change is determined.

Foaming moldability (small number of large bubbles ) A foam body is sliced into 2 mm thick, and 1 mm or more bubbles are formed.
Count the number in 00m ² . Compressive strain recovery foam is cut into 50mm x 50mm, thickness 25mm, and the test piece is placed between parallel flat plates of compression tester, 10mm / mi
Compress at a speed of n until a load of 5 kg / cm ² is reached and stop. After stopping for 20 seconds, the test piece is removed from the flat plate and left for 1 hour, and then the thickness is measured. Compression recovery rate (%) = 100 × t ₁ / t ₀ t ₀ : initial thickness of test piece (mm) t ₁ : thickness of test piece after test (mm) 98% or more ... ◎ 95 to 98% Less than ... ○ 90 to 9
Less than 5% ... △ Less than 90% ... ×

An adhesive foam having a square shape with a side of 50 mm is prepared. It adheres to a base plate plywood using an epoxy adhesive. The bonded test piece is subjected to the following JAS plane tensile test. A metal plate having a square-shaped bonding surface with one side of 20 mm in the center of the surface of the test piece was bonded using a cyanoacrylate adhesive, and a 5 mm Conduct a tensile test in minutes. Punchability A vinyl chloride plate having a thickness of 2 mm is adhered to the upper and lower surfaces of a foam having a side of 200 mm (thickness of 20 mm) using an epoxy adhesive. The bonded test piece is checked for punching property by a punching machine. [Evaluation Criteria for Punchability] Both foam and vinyl chloride plate are not deformed ... ◎ Both foam and vinyl chloride plate are not deformed, but the cut surface is crispy ... ○ Foam or vinyl chloride plate is slightly deformed… △ Foam , Vinyl chloride plate is deformed… ×

The symbols in the table have the following meanings. LLDPE-1
Reference numerals 2 and 2 are linear low-density polyethylene, respectively, Sumikasen-L manufactured by Sumitomo Chemical Co., Ltd. EVA-1 and EVA-2 are ethylene-vinyl acetate copolymers, and are vertates of Sumitomo Chemical Co., Ltd., respectively. VA indicates vinyl acetate content. For BLDPE, the blending ratio of branched low-density polyethylene is a value obtained from (C × s) / (A + B × 3). The specific surface area is a value obtained by the air permeation method. The blending amount of each component in the table is parts by weight.

[0015]

[Table 1] Table-1 ─────────────────────────────────── Component 1 2 3 4 5 6 ─────────────────────────────────── LLDPE-1 (Density 0.93g / cm ³ , MI = 1) 55 60 LLDPE-2 (Density 0.92g / cm ³ , MI = 1.5) 57 60 40 60 EVA-1 (VA = 5%) 10 8 10 4 EVA-2 (VA = 10%) 5 9 Heavy calcium carbonate- 1 30 30 30 23 30 32 (Specific surface area 3m ² / g) Heavy calcium carbonate-2 (Specific surface area 1.5m ² / g) BLDPE (Density 0.91g / cm ³ , MI = 2) 5 15 Azodicarbonamide 4 4 3 3 4 3 1,3-bis (tertiary butyl 0.5 0.5 0.5 0.5 0.5 0.5 oxyisopropyl) benzene calcium stearate 0.1 0.1 0.1 0.1 0.1 0.1 zinc oxide 0.4 0.4 0.4 0.4 0.4 0.4 ──────────── ──────────────────────── Mixing ratio 1.06 1.20 0.96 0.82 1.28 1.33 ────────────────── ── ─────────────── Heat resistance ◎ ◎ ◎ ○ ○ ◎ Foam moldability (small number of large cells) ◎ ◎ ◎ ◎ ◎ ◎ ◎ Compressive strain recovery ◎ ◎ ◎ ◎ ◎ ◎ ○ Adhesion ◎ ◎ ◎ ◎ ◎ ◎ ○ Punching performance ◎ ◎ ◎ ○ ○ ○ ────────────────────────────────────

[0016]

[Table 2] Table-2 ─────────────────────────────────── Component 7 8 9 10 ── ───────────────────────────────── LLDPE-1 (Density 0.93 g / cm ³ , MI = 1) 50 50 LLDPE-2 (Density 0.92g / cm ³ , MI = 1.5) 45 29 EVA-1 (VA = 5%) 15 10 8 EVA-2 (VA = 10%) 12 Ground calcium carbonate-1 25 38 55 (ratio Surface area 3 m ² / g) Heavy calcium carbonate -2 35 (Specific surface area 1.5 m ² / g) BLDPE (Density 0.91 g / cm ³ , MI = 2) 10 Azodicarbonamide 4 4 3 3 1,3-bis (Tasha Li-butyl 0.5 0.5 0.5 0.5 Oxyisopropyl) benzene Calcium stearate 0.1 0.1 0.1 0.1 Zinc oxide 0.4 0.4 0.4 0.4 ───────────────────────────── ─────── Mixing ratio 0.83 0.66 1.54 2.53 ─────────────────────────────────── Heat resistance ○ ◎ ◎ Foaming moldability (small number of large bubbles) ○ ○ ◎ ○ Compressive strain recovery property ○ ◎ ◎ ○ Adhesion ◎ ○ ◎ ◎ Punching property ○ ○ ◎ ◎ ───────────── ──────────────────────

[0017]

[Table 3] Table-3 (Comparative example) ─────────────────────────────────── Component 11 12 13 14 15 16 ─────────────────────────────────── LLDPE-1 23 76 26 72 58 44 EVA- 1 (VA = 5%) 14 4 5 10 20 2 Heavy calcium carbonate-1 58 16 65 14 18 50 (Specific surface area 3 m ² / g) Heavy calcium carbonate-3 (Specific surface area 1 m ² / g) BLDPE Light carbonic acid Calcium (Specific surface area 5 m ² / g) Azodicarbonamide 4 3 3 3 3 3 3, 1,3-bis (tertiary butyl 0.5 0.5 0.5 0.5 0.5 0.5 oxyisopropyl) benzene Calcium stearate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Zinc oxide 0.4 0.4 0.4 0.4 0.4 0.4 ─────────────────────────────────── Mixing ratio 2.67 0.54 4.76 0.41 0.45 3.00 ──── ── ──────────────────────────── Heat resistance △ ○ ○ ○ × ○ Foam moldability (small number of large cells) △ △ △ × △ △ Compressive strain recovery ○ ○ × × × × Adhesive ◎ × △ △ ◎ × Punching △ × △ × △ △ ────────────────────── ─────────────

[0018]

[Table 4] Table-4 (Comparative example) ─────────────────────────── Component 17 18 19 ──────── ──────────────────── LLDPE-1 40 55 EVA-1 (VA = 5%) 10 10 10 Heavy calcium carbonate-1 30 (Specific surface area 3 m ² / g) heavy calcium carbonate -3 30 (specific surface area 1 m ² / g) BLDPE 55 precipitated calcium carbonate 45 (specific surface area 5 m ² / g) azodicarbonamide 4 4 4 1,3-bis (tert-butyl 0.5 0.5 0.5 oxy (Isopropyl) benzene Calcium stearate 0.1 0.1 0.1 Zinc oxide 0.4 0.4 0.4 ─────────────────────────── Mixing ratio 3.00 3.21 0.35 ───── ────────────────────── Heat resistance △ △ △ Foaming moldability (small number of large cells) △ × × Compressive strain recovery ○ △ adhesion ○ △ △ punching properties × △ △ ───────────────────────────

Claims (4)

[Claims] 1. (A) Linear low-density polyethylene 25-
75% by weight, (B) ethylene vinyl acetate copolymer 3 to
A polyolefin resin crosslinked foam comprising 18% by weight and (C) 15 to 60% by weight of an inorganic filler having a specific surface area of 1.5 to ⁴ m ² / g. 2. The foam according to claim 1, which contains components A, B and C within the range represented by the following formula. 0.6 <(C × s) / (A + B × 3) <2.6 (wherein A, B and C are% by weight in the foam of components A, B and C, s is the specific surface area of component C) (M ² / g).) 3. The foam according to claim 1, wherein the component B is an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 10% and a melt flow rate of 1 to 3 g / 10 minutes. 4. The foam according to claim 1, wherein the component C is a heavy calcium carbonate having a specific surface area of 2 to 3 m ² / g, and the content thereof is 30 to 50% by weight.