JPH03146533A - Composition for polyolefin crosslinked foam - Google Patents

Abstract

PURPOSE:To provide the title composition capable of giving flexible and uniform crosslinked foams, fine pores, good in mechanical properties, comprising a polyolefin, a decomposable organic foaming agent and a stearyl calcium lactate. CONSTITUTION:The objective composition comprising (A) 100 pts.wt. of a polyolefin (pref. PE or PP), (B) pref. 3-30 pts.wt. of a decomposable organic foaming agent (e.g. azodicarbonamide), and (C) pref. 0.2-5.0 pts.wt. of a stearyl calcium lactate of the formula ((n) is 1-5).

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a composition for a crosslinked polyolefin foam, and in particular a crosslinked polyolefin composition that provides a foam having uniform, fine cells, flexibility, and good mechanical properties. The present invention relates to a composition for foam.

[Prior art and problems to be solved by the invention] Polyolefin foams have excellent mechanical strength, flexibility, texture, heat resistance, chemical resistance, etc., and are used as interior materials for automobiles, insulation materials,
It is widely used in cushioning materials for sporting goods and food packaging, as well as other sound-deadening materials and exterior materials.

In such foams, foaming conditions such as the type of polyolefin, molding method, foaming ratio, and pressure often differ. In order to meet these foaming conditions, a foaming aid is added when the foaming agent alone is insufficient.

For example, foaming accelerators such as zinc oxide, lead carbonate, lead oxide, barium stearate, magnesium oxide, citric acid, urea, sand, and ethanolamine are added to organic decomposable blowing agents. Adjusting the decomposition conditions.

However, the above-mentioned foaming accelerators do not have sufficient compatibility with polyolefins, so they are unevenly dispersed in the polyolefins, and the blowing agents are partially not completely decomposed, resulting in non-uniform cell diameters. Also, there was a problem that the bubbles became coarse.

This has been a cause of deteriorating the mechanical properties, flexibility and uniformity of the resulting foam.

Therefore, an object of the present invention is to provide a composition for a crosslinked polyolefin foam that has fine, uniform cells, is flexible, and has good mechanical properties.

[Means to solve the problem]

As a result of intensive research in view of the above issues, the present inventors have found that calcium stearyl lactate, which is used as a bread improving agent, has good compatibility with polyolefins and acts as a foaming accelerator to completely eliminate the foaming agent. It was discovered that the foam obtained by adding it has fine and uniform cells, and the present invention was conceived based on this discovery.

That is, the composition for a crosslinked polyolefin foam of the present invention is characterized by containing a polyolefin, an organic decomposable foaming agent, and calcium stearyl lactate.

The present invention will be explained in detail below.

In the present invention, the polyolefin includes ethylene,
Homopolymers of Φ olefins such as propylene, butene-11hexene-L, 4methylpentene-■, copolymers of ethylene and propylene or other diolefins, copolymers of two or more of these olefins, etc. can be used. Among these are low density polyethylene,
Polyethylene and polypropylene, such as linear low density polyethylene, medium density polyethylene, and high density polyethylene, are preferred. Polypropylene is not limited to a homopolymer, and the propylene component is 50 mol% or more, preferably 80 mol%
Random or block copolymers with other α-olefins including those mentioned above can also be used. Comonomers copolymerized with propylene include ethylene and other diolefins, with ethylene being particularly preferred. Therefore, the term "polypropylene" used herein is not limited to homopolymers of propylene, but should be understood to include copolymers as well.

In the present invention, the organic decomposable blowing agent is a compound that is liquid or solid at room temperature, but decomposes or vaporizes when heated above the melting point of the polyolefin used.
Any material can be used as long as it does not substantially interfere with molding such as sheeting or crosslinking reaction, but those with a decomposition temperature of 180 to 2
A temperature range of 70°C is preferred. Specific examples include azodicarbonamide, azodicarboxylic acid metal salts,
dinitrosopentamethylenetetramine, hydrazodicarbonamide, ρ-toluenesulfonyl semicarbazide,
S-) lyhydrazinotriazine and the like.

The organic decomposable blowing agent mentioned above is usually polyolefin 100
3 to 30 parts by weight, preferably 5 to 20 parts by weight
It is used within the range of parts by weight, and the amount added can be arbitrarily changed depending on the type and expansion ratio.

In the present invention, calcium stearyl lactate added as a foaming promoter is represented by the following structural formula.

C(13 CH.

[However, n in the formula is an integer from 1 to 5, and usually n=2
It is. ] The above calcium stearyl lactate is added in an amount of 0.2 to 5.0 parts by weight, preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of Poly 11F4F. Alternatively, the amount added can be arbitrarily changed depending on the type of foaming agent and the foaming ratio.

For example, when azodicarbonamide is used as a foaming agent, the amount of calcium stearyl lactate added is approximately 0.3 parts by weight if the desired expansion ratio is 5 times, and approximately 0.5 parts by weight if the desired expansion ratio is 10 times. If it is 15 times, it is about 0.7 part by weight, and if it is 30 times, it is about 1.0 part by weight.

In the present invention, in addition to the above-mentioned components, a peroxide can be added in order to perform a crosslinking reaction.

However, when the crosslinking reaction is carried out by irradiation with radiation, it is not necessary to use an organic peroxide. When using an organic peroxide, for example, when polypropylene or polyethylene is used as the polyolefin, the decomposition temperature is about 150
℃ or higher, specific examples include methyl ethyl ketone peroxide (182℃), t-butylperoxyisopropyl carbonate (153℃), dicumyl peroxide (17℃), cumene hydroperoxide (255℃). , 2゜5-dimethyl-2,5-di(t
-butylperoxy)hexane (179°C), 2.5-
Examples include dimethyl-2,5-di(t-butylperoxy)hexyne-3 (193°C) and di-t-butylperoxyphthalate (159°C). These organic peroxides are used in an amount of 0.02 to 2.0 parts by weight per 100 parts by weight of polyolefin.
It is used in an amount of 0 parts by weight, preferably 0.05 to 1.5 parts by weight.

Further, in order to carry out the crosslinking reaction smoothly and efficiently, it is preferable to add a crosslinking aid. Examples of crosslinking aids that can be used in the present invention include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol pentaacrylate, diallyl phthalate, diallyl maleate, and the like. When using an organic peroxide for crosslinking, the amount of crosslinking aid added is 0.05 to 5.0 parts by weight, preferably 0.1 to 3.0 parts by weight, per 100 parts by weight of the polyolefin. .

In other car inventions, various other compounding agents, specifically rubber substances, other resins, pigments, various fillers, flame retardants, antioxidants, etc., are used to improve the properties of polyolefin. can be mixed as appropriate.

The composition for a crosslinked polyolefin foam of the present invention comprises the above-mentioned polyolefin, a blowing agent, calcium stearyl lactate, an organic peroxide blended as necessary,
It can be obtained by kneading a crosslinking aid, other compounding agents, etc. using a kneader, Henschel mixer, extruder, etc. The kneading temperature is preferably set appropriately depending on the base polyolefin.

Moreover, crosslinking and foaming of this composition can be performed as follows.

First, the above-mentioned kneaded material is extruded into a predetermined shape using a die such as an extruder. At this time, the extrusion temperature is appropriately controlled depending on the base polyolefin.

The molded body thus obtained is then crosslinked,
As for the formation method of the crosslinked structure, in addition to the method using organic peroxide as mentioned above, there are conventional methods such as irradiation with ionizing radiation such as alpha rays, beta rays (electron beams), and γ rays, and methods using heating. The method described can be adopted. Among these methods, a method by irradiation with ionizing radiation is preferred, and crosslinking by electron beam irradiation is particularly preferred. The amount of radiation irradiated varies depending on the type and amount of organic peroxide and crosslinking aid, and the degree of crosslinking, but is generally 0.1 to 50 Mr.
ad, preferably 1 to 30 Mrad.

The thus crosslinked composition of the present invention can be foamed by heating it to a temperature higher than the melting point of the resin component. For example, when polypropylene is used as the polyolefin, 200°C or higher, preferably 230-38°C
This can be done by heating to a temperature of 0°C. The heating time required for foaming is usually 0.5 to 5 minutes.

[For production]

In the present invention, a composition for polyolefin crosslinked foam is prepared by adding calcium stearyl lactate as a foaming promoter.

The foam of this composition is flexible and has good mechanical properties.

The reason why the composition of the present invention has such characteristics is that calcium stearyl lactate is well compatible with polyolefin, and also has the effect of promoting foaming and uniformly dispersing the organic decomposable foaming agent. This is thought to be because the organic decomposable foaming agent foams completely and uniformly, resulting in a foam having fine and uniform cells.

〔Example〕

The present invention will be explained in more detail by the following specific examples.

In each of the Examples and Comparative Examples, the following resins were used as raw material resins.

[11 Polypropylene/RPP: Propylene-ethylene lanter AJ4 [combined [F4098B, manufactured by Tonen Petrochemical @, melt flowray] (MFR, 230°C, 2.16 kg load) 9 g/
lo: Ethylene content 3.5% by weight] [21 Linear low density polyethylene LLDPE: [GML2612, manufactured by Nippon Unicar@, melt index (Ml, 190
°C, 2.16 kg load) 12 g/10 minutes] [3] Low density polyethylene LDP E: [DFOIN, manufactured by Nippon Unicar ■, melt index (Ml, 190 °C, 2.1
6 kg load) 3 g/10 minutes] [4] High-density polyethylene/HDPE: CJ6311, manufactured by Tonen Petrochemical @, Melt Index (formerly, 190°C, 2.16 kg load) 9 g/10 minutes] [5] Foaming accelerator ( 1) Calcium stearyl lactate/shia-Ca-3t: [MC3TAB LA^,
(manufactured by Ciba Geigy)] (2) Lactic acid/La: [Musashino lactic acid, manufactured by Musashino Geigy ■] (3) Zinc oxide/ZnO: [American style zinc oxide No. 3, manufactured by Sakai Kagaku ■] Example 1 Shown in Table 1 Calcium stearyl lactate was added to polypropylene at a blending ratio, and 15 parts by weight of azodicarbonamide (manufactured by Hydraulic Chemical @) was added as a blowing agent, and trimethylolpropane trimethacrylate was added as a crosslinking agent.
(Shin Nakamura Chemical @l) 1.0 ff1IN and 0.3 tetrakis[methylene 3(3,5-di-sabtyl-4-hydroxyphenyl)propionate comethane (Irganoxlolo, manufactured by Ciba Geigy) as an antioxidant.
parts by weight and heated to 30°C using a Henschel mixer.
, after mixing for 2 minutes at 500 rpm, 5 with T-die
0 mmφ, length/diameter (L/D) = 28, and extruded at an extrusion temperature of 160°C to a thickness of 1. Omm
A sheet was created.

Next, a 750 kV electron beam was applied to this sheet at 8 Mrad.
was irradiated at a dose of Afterwards, it was placed in an air oven at 250℃ for 1.5 minutes to decompose the foaming agent.
Foamed twice as much.

The gel fraction, density after foaming, tensile strength at 23° C., tensile elongation and tear strength, compressive strength and compression set were measured for the polypropylene crosslinked foam sheet thus obtained.

The compressive strength and compression set rate can indicate the flexibility of the foam, and the smaller the value of the compressive strength, the more flexible and elastic the material is. The smaller the value, the more flexible it is.

The compression strength and compression set rate were measured on a foam sheet with a thickness of 13 mm formed by stacking foam sheets.

In addition, the state of the bubbles and the average bubble diameter of the foamed sheet were observed visually and with a microscope.

The results are also shown in Table 1.

Comparative Example 1 A polypropylene crosslinked foam sheet was prepared in the same manner as in Example 1 except that 1.5 parts by weight of lactic acid was used instead of 1.0 parts by weight of calcium stearyl lactate as a foaming promoter, and the gel fraction and foaming were The subsequent density, tensile strength, tensile elongation and tear strength at 23°C, compressive strength and compression set were measured, respectively. In addition, the state of the bubbles and the average bubble diameter were observed.

The Song Dynasty is also shown in Table 1.

Example 2 Calcium stearyl lactate was added to polypropylene and linear low density polyethylene at the blending ratio shown in Table 1,
Furthermore, as a blowing agent, azodicarbonamide (Hydration Chemical)
(manufactured by Shin Nakamura Kagaku ■) and 1.0 parts by weight of trimethylolpropane trimethacrylate (manufactured by Shin Nakamura Kagaku ■) as a crosslinking aid.
parts by weight, and tetrakis [methylene-3] as an antioxidant.
(3,5-di-t-butyl-4-hydroxyphenyl)
0.3 IN part of propionate comethane (Irganoxlolo, manufactured by Ciba Geigy) was added and mixed for 2 minutes at 30°C and 500 rpm using a Henschel mixer.
) = 28 extruder and extruded at an extrusion temperature of 160°C to create a sheet with a thickness of 0 mm.

Next, a 750 kV electron beam was applied to this sheet at 8 Mrad.
was irradiated at a dose of Afterwards, it was placed in an air oven at 250℃ for 1.5 minutes to decompose the foaming agent.
Foamed twice as much.

The gel fraction, density after foaming, tensile strength at 23° C., tensile elongation and tear strength, compressive strength, and compression set were measured for the crosslinked foam sheet thus obtained. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

Comparative Example 2.3 A crosslinked foam sheet was prepared in the same manner as in Example 2, except that 1.5 parts N of lactic acid was used instead of 1.0 parts IH of calcium stearyl lactate as the foaming accelerator. And so. In addition, a crosslinked foam sheet was prepared in the same manner as Comparative Example 3 except that 0.02 parts by weight of zinc oxide was used.

For these foamed sheets, the gel fraction, density after foaming, tensile strength at 23°C, tensile elongation and tear strength, compressive strength, and compression set were measured, respectively. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

Example 3 Calcium stearyl lactate was added to linear low-density polyethylene and low-density polyethylene in the proportions shown in Table 1, and 15 parts by weight of azodicarbonamide (manufactured by Hydration Kagaku@) as a blowing agent and a crosslinking agent were added. 0 parts by weight of trimethylolpropane trimethacrylate (manufactured by Shin Nakamura Kagaku@) as an agent, and tetrakis [methylene-3 (
0.3 parts by weight of 3,5-di-t-butyl-4-hydroxyphenyl)propionate comethane (lrganoxlolo, Baby Geigy M) was added and mixed for 2 minutes at 30°C and 500 rpm using a Henschel mixer. After, 50mmφ with T die, length/diameter (L/D)
-28 extruder and extruded at an extrusion temperature of 140°C to a thickness of 1. A sheet of Omm was created.

Next, a 750 kV electron beam was applied to this sheet at 6 Mrad.
was irradiated at a dose of Afterwards, it was placed in an air oven at 250℃ for 1.5 minutes to decompose the foaming agent.
Foamed twice as much.

The gel fraction, density after foaming, tensile strength at 23° C., tensile elongation and tear strength, compressive strength, and compression set were measured for the crosslinked foam sheet thus obtained. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

Comparative Example 4.5 A crosslinked foam sheet was prepared in the same manner as in Example 3 except that 1.5 parts by weight of lactic acid was used instead of 1.0 parts by weight of calcium stearyl lactate as a foaming accelerator. did. In addition, a crosslinked foam sheet was prepared in the same manner as Comparative Example 5 except that 0.02 parts by weight of zinc oxide was used.

For these foamed sheets, the gel fraction, density after foaming, tensile strength at 23°C, tensile elongation and tear strength, compressive strength, and compression set were measured, respectively. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

Example 4 Calcium stearyl lactate was added to linear low-density polyethylene in the proportions shown in Table 1, and 15 parts by weight of azodicarbonamide (manufactured by Hydraulic Chemical @) was added as a blowing agent, and trimethylol was added as a crosslinking aid. Propane trimethacrylate (Shin Nakamura Chemical ■a> t, o 1 part and as an antioxidant tetrakis [methylene: 1 l (3,5-
dibutyl-4-hydroxyphenyl) propionate comethane (Iγganox lθ10, Ciba Geigy)
ffi) and mixed for 2 minutes using a Henschel mixer at 30t and 500rpm.
50mmφ with die, length/diameter (L/D)=
213117) [11,: Feeding and extrusion temperature 140 t
Extrude and thicken! , Omm sheets were created.

Next, a 750 kV electron beam was applied to this sheet at 6 Mrad.
was irradiated at a dose of After that, it was placed in a 250 t air oven for 1.5 minutes to decompose the foaming agent, and the
It was foamed 0 times.

The gel fraction, density after foaming, tensile strength at 23° C., tensile elongation and tear strength, compressive strength, and compression set were measured for the crosslinked foam sheet thus obtained. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

Example 5 Calcium stearyl lactate was added to high-density polyethylene in the proportions shown in Table 1, and 15 parts by weight of azodicarbonamide (manufactured by Hydraulic Chemical Co., Ltd.) as a blowing agent and trimethylolpropane trimethyl as a crosslinking agent were added. 1.0 parts by weight of methacrylate (manufactured by Shin Nakamura Kagaku ■) and tetrakis [methylene-3 (3,5-di-sabtyl-4-hydroxyphenyl) propionate comethane] as an antioxidant.
Add 0.3 parts by weight of Irganoxlθ10 (Ciba Geigy Kai) and mix at 30°C for 5 minutes using a Henschel mixer.
After mixing for 2 minutes at 00 rpm, 50 m with T-die
mφ, length/diameter (L/D) = 28, fed to an extruder,
It was extruded at an extrusion temperature of 140°C to create a sheet with a thickness of 1.0 mm.

Next, a 750 kV electron beam was applied to this sheet at 6 Mrad.
was irradiated at a dose of After that, it was placed in an air oven at 250℃ for 1.5 minutes to decompose the foaming agent.
Foamed twice as much.

The gel fraction, density after foaming, tensile strength at 23° C., tensile elongation and tear strength, compressive strength, and compression set were measured for the crosslinked foam sheet thus obtained. In addition, the state of the bubbles and the average bubble diameter were observed.

The results are also shown in Table 1.

(1) This is a value measured according to JIS K6767, and shows the value in the direction (MO) 7 width direction (TO).

(2) It is a value measured according to JIS K6767, and shows the value in the direction (MO) 7 width direction (TO).

(3) It is a value measured according to JIS K6767, and shows the value in direction (■) 7 width direction (TO).

(4) Value measured according to JIS K6767.

(5) This is a value measured according to JIS 6767, and indicates the compression set rate (%).

From the above results, the values of tensile strength, tensile elongation, and tear strength of the crosslinked foam sheets of each example are larger than those of the corresponding comparative examples, and the compressive strength and It can be seen that the value of the compression set is small, and the foam made from the composition of the present invention has excellent strength and flexibility.

Moreover, the average cell diameter of the crosslinked foam sheet made from the composition of the present invention is 0.3 to 0.4 mm, which is uniform and fine.

On the other hand, in each comparative example, as a foaming accelerator,
In the case where lactic acid was used, the bubble diameter was non-uniform, and in the case where zinc oxide was used, the bubbles were coarse.

In the above examples, the case where the composition of the present invention was molded into a sheet was explained, but the composition of the present invention is not limited to this, and can be made into foams of various shapes.

〔Effect of the invention〕

As detailed above, since the composition for polyolefin crosslinked foam of the present invention contains calcium stearyl lactate as a foaming promoter, the foaming agent is uniformly dispersed and completely decomposed. Therefore, the crosslinked foam made from the composition of the present invention has uniform and fine cells, is flexible, and has good mechanical properties.

Applicant: Tonen Petrochemical Co., Ltd.

Claims (2)

[Claims] (1) A composition for a crosslinked polyolefin foam, characterized by containing a polyolefin, an organic decomposable foaming agent, and calcium stearyl lactate. (2) In the composition for a polyolefin crosslinked foam according to claim 1, 3 to 30 parts by weight of the organic decomposable blowing agent and 0.2 to 5 parts by weight of the calcium stearyl lactate are contained, based on 100 parts by weight of the polyolefin. A composition for a crosslinked polyolefin foam, characterized in that it contains 0 parts by weight.