JP2021054956A - Polyolefin-based resin non-crosslinked extrusion molding, and cushioning material - Google Patents

Abstract

To provide a new polyolefin-based resin non-crosslinked extrusion molding and cushioning material which are small in air bubble diameter and have excellent weather resistance.SOLUTION: A polyolefin-based resin non-crosslinked extrusion molding contains a polyolefin-based resin and a specific foam nucleus forming agent and a specific hindered amine-based photostabilizer on a specific condition, and has an expansion ratio of 3 times or more.SELECTED DRAWING: None

Description

The present invention relates to a polyolefin-based resin non-crosslinked extruded foam and a cushioning material.

Polyolefin-based resin foams are widely used as cushioning materials (for example, cushioning materials for packaging) because they are relatively excellent in flexibility and abrasion resistance. Polyolefin-based resin foams include bead foams, crosslinked batch foams, non-crosslinked extruded foams, and the like, depending on the manufacturing method.

Some bead foams have excellent wear resistance. However, the bead foam has a concern that the foamed beads may fall off. Foamed beads that fall off cause contamination. Therefore, the use of the beaded foam may be restricted from the viewpoint of preventing contamination.

Since the crosslinked batch foam has excellent properties such as abrasion resistance and heat resistance, it is widely used not only as a cushioning material but also as a vehicle interior material, industrial heat insulating material, sports equipment, etc. ing. However, the crosslinked batch foam has a problem that the production cost is high because an extra step for crosslinking is required. Further, since the crosslinked batch foam is crosslinked, it cannot be returned to the original resin and reused, and as a result, it is not suitable for the current recycling society. In particular, with respect to the polyethylene-based resin foam, the polyethylene-based resin crosslinked batch foam has a drawback that the processability is poor because the heat-sealing property is inferior to that of the polyethylene-based resin non-crosslinked extruded foam.

On the other hand, the polyolefin-based resin non-crosslinked extruded foam produced by the extrusion method has many merits such as no possibility of foam beads falling off, recyclability, and good heat-sealing property. Polyolefin-based resin non-crosslinked extruded foam has been put into practical use as a cushioning material for packaging. However, all of the conventionally used polyolefin-based resin non-crosslinked extruded foams have a large bubble diameter, and as a result, transfer of a bubble pattern occurs, and the bubbles have a hard tactile sensation as compared with a fine foam. Therefore, it tends to be avoided in some fields. Therefore, the present inventors have proposed a non-crosslinked polyethylene-based resin foam having a fine bubble diameter and excellent cushioning property (Patent Document 1).

Japanese Unexamined Patent Publication No. 2019-0019666

By the way, the polyolefin-based resin foam may be stored outdoors for a long period of time. Therefore, the polyolefin-based resin foam is required to have weather resistance. However, the above-mentioned prior art has room for further improvement from the viewpoint of weather resistance.

One embodiment of the present invention has been made in view of the above problems, and an object thereof is a novel polyolefin resin non-crosslinked extruded foam and cushioning material having a small bubble diameter and excellent weather resistance. Is to provide.

As a result of diligent studies to solve the above problems, the present inventors have made no novel polyolefin-based resin having a small bubble diameter and excellent weather resistance by using a hindered amine-based light stabilizer under specific conditions. They have found that they can provide crosslinked extruded foams and cushioning materials, and have completed the present invention.

That is, one embodiment of the present invention includes the following configurations.
[1] Contains a polyolefin-based resin, a bubble nucleating agent containing a heat-decomposable foaming agent and an organic acid (salt), and a hindered amine-based light stabilizer that satisfies any of the following conditions (a) to (c). However, the polyolefin-based resin non-crosslinked extrusion foam having a foaming ratio of 3 times or more: Condition (a): The hindered amine-based photostabilizer does not contain or contains one secondary amino group in one molecule, and The content of the hindered amine-based light stabilizer is 0.001 part by weight to 3.000 parts by weight with respect to 100 parts by weight of the polyolefin-based resin; Condition (b): Weight average of the hindered amine-based light stabilizer. The molecular weight is 1,500 or less, and the content of the hindered amine-based light stabilizer is 0.001 part by weight to 3.000 parts by weight with respect to 100 parts by weight of the polyolefin-based resin; condition (c). : The hindered amine light stabilizer contains two or more secondary amino groups in one molecule, the weight average molecular weight of the hindered amine light stabilizer is more than 1,500, and the content of the hindered amine light stabilizer is However, it is 0.001 part by weight to 0.150 part by weight with respect to 100 parts by weight of the polyolefin resin.
[2] The polyolefin-based resin non-crosslinked extruded foam according to [1], wherein the polyolefin-based resin non-crosslinked extruded foam has an average cell diameter of 100 μm to 600 μm.
[3] The polyolefin-based resin non-crosslinked extruded foam according to [1] or [2], wherein the polyolefin-based resin non-crosslinked extruded foam has a thickness of 20 to 160 mm.
[4] The polyolefin-based resin non-crosslinked extruded foam according to any one of [1] to [3], wherein the polyolefin-based resin contains a polyethylene-based resin.
[5] The polyolefin-based resin non-crosslinked extruded foam according to [4], wherein the polyethylene-based resin contains 50% by weight or more of branched low-density polyethylene in 100% by weight of the polyethylene-based resin.
[6] The polyolefin-based resin non-crosslinked extruded foam according to any one of [1] to [5], wherein the polyolefin-based resin non-crosslinked extruded foam has a closed cell ratio of 70% or more.
[7] A cushioning material containing the polyolefin-based resin non-crosslinked extruded foam according to any one of [1] to [6].

According to one embodiment of the present invention, it is possible to provide a polyolefin-based resin non-crosslinked extruded foam and a cushioning material having a small bubble diameter and excellent weather resistance.

An embodiment of the present invention will be described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications can be made within the scope of the claims. The technical scope of the present invention also includes embodiments or examples obtained by appropriately combining the technical means disclosed in the different embodiments or examples. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. In addition, all the academic documents and patent documents described in the present specification are incorporated as references in the present specification.

Unless otherwise specified in the present specification, "A to B" representing a numerical range is intended to be "A or more (including A and larger than A) and B or less (including B and smaller than B)".

Unless otherwise specified in the present specification, the structural units include _{a structural unit derived from an X 1} monomer, a structural unit derived from an X ₂ monomer, ..., And an X _n monomer (n is 2 or more). A copolymer containing (an integer of) is also referred to _{as an X 1} / X ₂ / ... / X _{n copolymer.} Unless otherwise specified, the X ₁ / X ₂ / ... / X _n copolymer is not particularly limited in the polymerization mode, and may be a random copolymer or a block copolymer. It may be a graft copolymer or a graft copolymer. Further, the structural unit derived from the X monomer may be referred to as an "X unit".

[1. Technical Thought of One Embodiment of the Present Invention]
The present inventors have diligently studied to solve the above-mentioned problems. As a result, (1) by using a pyrolysis type foaming agent and a bubble nucleating agent containing an organic acid (salt), the bubble diameter of the foam can be reduced even if the foam has a large thickness. The present inventors have independently found that the weather resistance can be imparted by using (2) a hindered amine-based light stabilizer. Furthermore, in the process of study, the present inventors independently found the following: When a bubble nucleating agent containing a pyrolytic foaming agent and an organic acid (salt) and a hindered amine-based light stabilizer were used, the hindered amine was used. Depending on the type and amount of the light stabilizer used, a polyolefin-based resin non-crosslinked extruded foam having a large bubble diameter may be obtained. Therefore, the present inventors have conducted further diligent studies on hindered amine-based light stabilizers. As a result, the present inventors prevented the expansion of the bubble diameter by using the hindered amine-based light stabilizer under specific conditions even when the bubble nucleating agent and the hindered amine-based light stabilizer were used. Moreover, it has been found that excellent weather resistance can be imparted, and the present invention has been completed.

[2. Polyolefin resin non-crosslinked extruded foam]
The polyolefin-based resin non-crosslinked extrusion foam according to one embodiment of the present invention includes a polyolefin-based resin, a bubble nucleating agent containing a heat-decomposable foaming agent and an organic acid (salt), and the following conditions (a) to ( A polyolefin-based resin non-crosslinked extruded foam containing a hindered amine-based light stabilizer satisfying any of c) and having a foaming ratio of 3 times or more: Condition (a): The hindered amine-based light stabilizer is contained in one molecule. It does not contain or contains one secondary amino group, and the content of the hindered amine-based light stabilizer is 0.001 part by weight to 3.000 parts by weight with respect to 100 parts by weight of the polyolefin-based resin. Condition (b): The weight average molecular weight of the hindered amine light stabilizer is 1,500 or less, and the content of the hindered amine light stabilizer is 0.001 with respect to 100 parts by weight of the polyolefin resin. By weight to 3.000 parts by weight; Condition (c): The hindered amine-based light stabilizer contains two or more secondary amino groups in one molecule, and the weight average molecular weight of the hindered amine-based light stabilizer is 1,500. The content of the hindered amine-based light stabilizer is 0.001 part by weight to 0.150 part by weight with respect to 100 parts by weight of the polyolefin-based resin.

The "polyolefin-based resin non-crosslinked extruded foam" may be referred to as a "foam". The "polyolefin resin non-crosslinked extruded foam according to one embodiment of the present invention" may be referred to as "the present foam".

Since the present foam has the above-mentioned structure, the bubble diameter is small. Further, since the present foam is an extruded foam, it has an advantage that there is less risk of contamination (contamination) as compared with a bead foam in which cracks and chips of beads may occur. Furthermore, since the present foam contains a hindered amine-based light stabilizer, it has excellent weather resistance. In other words, this foam can be used for a long period of time as a high-quality cushioning packaging material with less risk of contamination because the generation of abrasion powder during transportation of parts, etc. is small even after it is stored outdoors. Become. Further, this foam is processed because (a) it does not need to be crosslinked, so it is excellent in cost and production efficiency, (b) it is not crosslinked, so it is excellent in recyclability, and (c) it is excellent in heat fusion property. It also has the effect of having good properties.

[Polyolefin-based resin]
The polyolefin-based resin is not particularly limited as long as it is a (co) polymer having a structural unit derived from an olefin such as ethylene, propylene, butadiene, isoprene or a diolefin (hereinafter referred to as a polymer (A)). .. The polyolefin-based resin is a (co) polymer having a structural unit derived from an olefin or a diolefin and a structural unit derived from an olefin or another monomer copolymerizable with the diolefin (hereinafter, a polymer). It may be (B). Other monomers copolymerizable with olefins or diolefins include (a) vinyl compounds such as vinyl acetate, vinyl chloride, acrylic acid, methacrylic acid and styrene, and (b) maleic anhydride, maleic acid and acrylic. Examples include unsaturated carboxylic acids such as acids. The polyolefin-based resin is a (co) polymer in which a (co) polymer having a structural unit derived from an olefin or a diolefin is graft-modified with a vinyl compound and a derivative such as an unsaturated carboxylic acid (hereinafter, polymer (C). ).) May be used. The polyolefin-based resin may be a mixture of two or more kinds selected from the group consisting of the above-mentioned polymer (A), polymer (B) and polymer (C).

Specific examples of the polyolefin-based resin include polyethylene-based resins and polypropylene-based resins. In one embodiment of the present invention, the polyolefin-based resin preferably contains a polyethylene-based resin and / or a polypropylene-based resin, and more preferably contains a polyethylene-based resin from the viewpoint of flexibility and abrasion resistance. It is more preferable that it is a based resin. As the polyolefin-based resin, one kind of resin may be used alone, or two or more kinds of resins may be used in combination.

Examples of the polypropylene-based resin include (co) polymers having 50 mol% or more of propylene-derived structural units in 100 mol% of all structural units. Specifically, as polypropylene-based resin, polypropylene homopolymer, polypropylene / ethylene block copolymer, polypropylene / ethylene random copolymer, propylene / α-olefin copolymer, propylene / 1-butene copolymer, ethylene / 1-butene / propylene copolymer, propylene / chlorinated vinyl copolymer, propylene / maleic anhydride copolymer, long-chain branched polypropylene with high melt tension, isoprene-modified polypropylene, polypropylene containing ultra-high molecular weight components, etc. Can be mentioned. The isoprene-modified polypropylene can be produced by a known method. As the polypropylene-based resin, one kind of resin may be used alone, or two or more kinds of resins may be used in combination. Since it is suitable for foaming, long-chain branched polypropylene having a high melt tension, isoprene-modified polypropylene, and polypropylene containing an ultra-high molecular weight component are preferable.

A case where the polypropylene-based resin contains a structural unit (ethylene unit) derived from ethylene such as a polypropylene / ethylene random copolymer will be described. In this case, the content of ethylene units in 100% by weight of the polypropylene resin is preferably 0.2% by weight or more and 10% by weight or less.

The density and MFR of the polypropylene resin are not particularly limited. The MFR of the polypropylene resin is preferably 0.5 g / 10 minutes to 20.0 g / 10 minutes, more preferably 1.0 g / 10 minutes to 15.0 g / 10 minutes, and 1.5 g / 10 minutes to 10. 0 g / 10 minutes is more preferable, and 2.0 g / 10 minutes to 8.0 g / 10 minutes is particularly preferable. According to this configuration, the raw material resin has a high melt tension and can prevent excessive shear heat generation in the extruder. As a result, there is an advantage that it tends to be easy to set conditions suitable for extrusion foaming.

The MFR of the polypropylene resin is a value obtained by measuring at 230 ° C. and a load of 2.16 kg according to JIS K-7210.

The melting point of the polypropylene resin is not particularly limited. The melting point of the polypropylene resin is preferably 125 ° C. to 163 ° C., more preferably 130 ° C. to 163 ° C., further preferably 133 ° C. to 163 ° C., and particularly preferably 135 ° C. to 163 ° C. According to this configuration, there is an advantage that it is easy to balance heat resistance and foamability.

The melting point of the polypropylene resin is measured by a differential scanning calorimetry method (hereinafter referred to as "DSC method"). The specific operation procedure is as follows: (1) After 5 to 6 mg of polyethylene resin is heated from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min and melted; (2) 10 After the temperature is lowered from 220 ° C. to 40 ° C. to crystallize at a temperature lowering rate of ° C./min; The temperature of the peak (melting peak) of the DSC curve obtained at the time of the second temperature rise (that is, at the time of (3)) can be obtained as the melting point.

Examples of the polyethylene-based resin include (co) polymers having 50 mol% or more of ethylene-derived structural units in 100 mol% of all structural units. Specifically, as polyethylene-based resins, high-density polyethylene, branched low-density polyethylene, ethylene / α-olefin copolymer, ethylene / vinyl acetate copolymer, ethylene / propylene copolymer, ethylene / propylene / 1- Butene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-methyl-1-pentene copolymer, ethylene / 1-octene copolymer, styrene-modified polyethylene-based Examples include resins. The branched low-density polyethylene can be said to be low-density polyethylene produced by the high-pressure method. The branched low density polyethylene is sometimes referred to as "LDPE".

A case where the copolymer, such as an ethylene / propylene copolymer, contains an ethylene unit and a propylene unit as a constituent unit will be described. In this case, a copolymer containing more ethylene units than propylene units is called a polyethylene resin, and a copolymer containing more propylene units than ethylene units is called a polypropylene resin.

Since the polyethylene-based resin is excellent in foamability, the polyethylene-based resin preferably contains 50% by weight or more of branched low-density polyethylene, more preferably 60% by weight or more, and 70% by weight or more, based on 100% by weight of the polyethylene-based resin. It is more preferably contained, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. According to this configuration, it has an advantage of being excellent in foamability.

Since the polyethylene-based resin is excellent in abrasion resistance and foamability, the polyethylene-based resin is 50% by weight to 95% by weight of branched low-density polyethylene and 5% by weight of an ethylene / α-olefin copolymer in 100% by weight of the polyethylene-based resin. It preferably contains ~ 50% by weight, more preferably 60% by weight to 90% by weight of branched low density polyethylene and 10% by weight to 40% by weight of ethylene / α-olefin copolymer, and more preferably branched low density polyethylene. It is more preferable to contain 70% by weight to 85% by weight of the density polyethylene and 15% by weight to 30% by weight of the ethylene / α-olefin copolymer.

The branched low-density polyethylene preferably has a density of 935 kg / m ³ or less. The lower limit of the density of the branched low-density polyethylene is not particularly limited, but is approximately 910 kg / m ³ . Because of its excellent balance between the foaming heat resistance, the density of the branched low density polyethylene is ^preferably from ^{910kg / m 3 ~935kg / m 3} , more preferably ^{911kg / m 3 ~930kg / m 3} , 912kg / m ^{3 to} 928 kg / m ³ is more preferable, and 913 kg / m ^{3 to} 926 kg / m ³ is particularly preferable.

The density of the ethylene / α-olefin copolymer is not particularly limited. Because of its excellent balance between the foaming heat resistance, the density of the linear low density polyethylene is ^preferably from ^{870kg / m 3 ~930kg / m 3} , more preferably ^{880kg / m 3 ~925kg / m 3} , 885kg / ^{m 3} ~920kg / m ³ more ^{preferably, 890kg / m 3 ~915kg / m} 3 is especially preferred. In the present specification, the density of the branched low-density polyethylene or ethylene / α-olefin copolymer is a value obtained by measuring according to JIS K-7112.

The MFR of the branched low density polyethylene is not particularly limited. The MFR of the branched low-density polyethylene is preferably 0.1 g / 10 minutes to 10.0 g / 10 minutes, more preferably 0.3 g / 10 minutes to 7.0 g / 10 minutes, and 0.5 g / 10 minutes to 5 minutes. .0 g / 10 minutes is more preferable, and 0.8 g / 10 minutes to 3.0 g / 10 minutes is particularly preferable. According to this configuration, the raw material resin has a high melt tension and can prevent excessive shear heat generation in the extruder. As a result, it tends to be easy to set conditions suitable for extrusion foaming.

The MFR of the ethylene / α-olefin copolymer is not particularly limited. The MFR of the linear low-density polyethylene is preferably 0.5 g / 10 minutes to 10.0 g / 10 minutes, more preferably 0.8 g / 10 minutes to 8.0 g / 10 minutes, and 1.0 g / 10 minutes to. 6.0 g / 10 minutes is more preferable, and 2.0 g / 10 minutes to 5.0 g / 10 minutes is particularly preferable. When the MFR of the ethylene / α-olefin copolymer is 0.5 g / 10 minutes or more, excessive shear heat generation in the extruder can be prevented. As a result, it tends to be easy to set conditions suitable for extrusion foaming. When the MFR of the ethylene / α-olefin copolymer is 10.0 g / 10 minutes or less, the obtained foam has high wear resistance.

In the present specification, the MFR of the branched low-density polyethylene or ethylene / α-olefin copolymer is a value obtained by measuring at 190 ° C. and a load of 2.16 kg according to JIS K-7210. Is.

As the polyethylene-based resin, one kind of resin may be used alone, or two or more kinds of resins may be used in combination. As the polyethylene-based resin, two or more kinds of resins having different densities may be used in combination. Examples of combinations of two or more types of polyethylene resins having different densities include a combination of branched low-density polyethylene and an ethylene / α-olefin copolymer.

The polyolefin-based resin preferably contains 50% by weight or more of branched low-density polyethylene, more preferably 60% by weight or more, more preferably 70% by weight or more, and 75% by weight, based on 100% by weight of the polyolefin-based resin. It is more preferable to contain% or more. According to this configuration, it has an advantage of being excellent in foamability.

The foam may contain a synthetic resin other than the polyolefin resin (for example, a thermoplastic resin and / or an elastomer) as long as the effect according to the embodiment of the present invention is not impaired. In the present specification, the polyolefin-based resin and the synthetic resin other than the polyolefin-based resin may be collectively referred to as a "raw material resin" or a "raw material resin component". Since the raw material resin or the raw material resin component accounts for at least 50% by weight or more in 100% by weight of the foam, it can be said to be a "main material".

Examples of synthetic resins other than polyolefin resins include (a) thermoplastic resins such as vinyl acetate resin, polyester resin, acrylic resin, acrylic acid ester resin, styrene resin, polyamide resin, polycarbonate resin, and polyvinyl chloride resin. , (B) Polyamide-based elastomers such as polyamide / polyol copolymers, and (c) Polyvinyl chloride-based elastomers, polybutadiene-based elastomers, ethylene / propylene rubbers, thermoplastic elastomers such as ethylene / propylene / butadiene rubbers, and the like. Be done.

The amount of the synthetic resin other than the polyolefin resin added in the production of the present foam, in other words, the content of the synthetic resin other than the polyolefin resin in the present foam is not particularly limited, and the effect according to one embodiment of the present invention. Can be set as appropriate as long as it does not interfere with the above. The addition amount (the content) of the synthetic resin other than the polyolefin resin is preferably 0 parts by weight to 30 parts by weight, more preferably 0 parts by weight to 15 parts by weight, for example, with respect to 100 parts by weight of the polyolefin resin. ..

In a foam produced using a raw material resin containing a polyolefin resin, the structure of the raw material resin changes, but the composition of the raw material resin does not change in principle. When the raw material resin contains a plurality of types of resins, it may be possible to specify the type and content ratio of the resin contained in the raw material resin by analyzing the foam.

[Bubble nucleation agent]
The bubble nucleating agent contained in the foam contains a pyrolytic foaming agent and an organic acid (salt). As used herein, the term "organic acid (salt)" means "organic acid and / or organic acid salt". When the bubble nucleating agent contains a pyrolytic foaming agent and an organic acid (salt), so that the bubble nucleating agent does not contain a pyrolyzing foaming agent and an organic acid (salt) but contains only an inorganic substance (for example, talc). The bubble diameter of the obtained foam can be reduced more easily as compared with the above. The bubble nucleating agent is more preferably composed of a mixture of a pyrolytic foaming agent and an organic acid (salt).

Examples of the pyrolytic foaming agent include ADCA (azodicarbonamide), DPT (N, N'-dinitropentamethylenetetramine), OBSH (4,4'-oxybisbenzenesulfonyl hydrazide), bicarbonate, and carbonate. And so on. As the pyrolytic foaming agent, a hydrogen carbonate, a carbonate, or a mixture of a hydrogen carbonate and a carbonate is preferable. Examples of the hydrogen carbonate include sodium hydrogen carbonate.

Examples of the organic acid (salt) include oxalic acid (salt), lactic acid (salt), succinic acid (salt), malic acid (salt), citric acid (salt) and the like. Citric acid (salt) is preferable as the organic acid (salt) because the effect of refining the cell diameter is high. Examples of citric acid (salt) include citric acid, monosodium citrate, trisodium citrate, sodium hydrogen citrate, potassium citrate and the like.

As a bubble nucleating agent, since it is easy to handle and has a high effect of forming bubble nuclei, a mixture of bicarbonate and citric acid (salt), a mixture of carbonate and citric acid (salt), and One or more mixtures selected from the group consisting of bicarbonate and a mixture of carbonate and citric acid (salt) are preferred, a mixture of bicarbonate and citrate is more preferred, sodium hydrogen carbonate and citric acid. A mixture with monosodium is particularly preferred.

The content ratio of the pyrolysis type foaming agent and the organic acid (salt) in the bubble nucleating agent is 10 for the pyrolysis type foaming agent, assuming that the total amount of the pyrolysis type foaming agent and the organic acid (salt) is 100% by weight. 90% to 90% by weight and 90% to 10% by weight of the organic acid (salt) are preferable, 20% to 85% by weight of the pyrolytic foaming agent and 80% to 15% by weight of the organic acid (salt). Is more preferable, and 30% by weight to 80% by weight of the pyrolytic foaming agent and 70% by weight to 20% by weight of the organic acid (salt) are further preferable. According to this configuration, there is an advantage that a nucleation effect can be easily obtained efficiently with a small amount of bubble nucleating agent.

In the production of the foam, the larger the amount of the bubble nucleating agent added, the smaller the bubble diameter of the obtained foam tends to be. In other words, the larger the content of the bubble nucleating agent in the foam, the smaller the bubble diameter of the foam tends to be. In the production of foam, the larger the amount of the bubble nucleating agent added, the higher the production cost and the higher the risk of foreign matter generation due to the decomposition products of the bubble nucleating agent. In the production of the foam, (a) the extruder is provided with a mesh for removing foreign matter in the extruder, and (b) the amount of the bubble nucleating agent added is large. In this case, the mesh in the extruder is clogged with the decomposed product of the bubble nucleating agent, which causes a problem such as an increase in pressure. As a result, frequent mesh replacement work is required, which reduces productivity. Therefore, the amount of the bubble nucleating agent added in the production of the present foam, in other words, the content of the bubble nucleating agent in the present foam is 0.03 parts by weight to 1. by weight with respect to 100 parts by weight of the polyolefin resin. 50 parts by weight is preferable, 0.08 parts by weight to 1.20 parts by weight is more preferable, and 0.10 parts by weight to 1.00 parts by weight is further preferable.

In the production of the present foam, the powdery bubble nucleating agent may be directly used as the bubble nucleating agent, and a masterbatch in consideration of mixing with the raw material resin component (main material) is used. Is also good. As the masterbatch of the bubble nucleation agent, a commercially available product can also be used, and examples thereof include Policelen EE275F manufactured by Eiwa Kasei Kogyo and Finecell Master SSC PO217K manufactured by Dainichiseika Kogyo.

[Hindered amine light stabilizer]
The foam contains a hindered amine light stabilizer (sometimes referred to as "HALS").

The present foam has a fine cell structure and excellent weather resistance by containing HALS under any of the following conditions (a) to (c). In other words, in the production of the present foam, when HALS is used under any of the following conditions (a) to (c), a fine cell structure is maintained and it has excellent weather resistance. A foam can be obtained.

Condition (a): The hindered amine-based light stabilizer does not contain or contains one secondary amino group in one molecule, and the content of the hindered amine-based light stabilizer is 100 parts by weight of the polyolefin-based resin. On the other hand, it is 0.001 part by weight to 3.000 parts by weight;
Condition (b): The weight average molecular weight of the hindered amine light stabilizer is 1,500 or less, and the content of the hindered amine light stabilizer is 0.001 weight by weight based on 100 parts by weight of the polyolefin resin. Parts to 3.000 parts by weight;
Condition (c): The hindered amine-based photostabilizer contains two or more secondary amino groups in one molecule, the weight average molecular weight of the hindered amine-based light stabilizer is more than 1,500, and the hindered amine-based photostabilizer is photostable. The content of the agent is 0.001 part by weight to 0.150 part by weight with respect to 100 parts by weight of the polyolefin resin.

Hereinafter, each condition will be described in detail.

Depending on the type and amount of HALS used, a foam having a larger cell diameter can be obtained as compared with the case where HALS is not used. In other words, the effect of increasing bubble nuclei by HALS is estimated as follows. it can. However, the present invention is not limited to the following speculations.

First, the effect of reducing the bubble diameter of the bubble nucleating agent will be considered. It is considered that there are two actions in the bubble diameter miniaturization effect of the bubble nucleating agent. The first action is the action of a pyrolytic foaming agent (pyrolytic chemical foaming agent). In the process of producing the foam, the pyrolytic foaming agent generates an inorganic gas having low solubility in a resin such as carbon dioxide. The inorganic gas vaporizes before the foaming agent used as the physical foaming agent. As a result, it is considered that the pyrolysis-type foaming agent can form a bubble growth point before the foaming agent used as the physical foaming agent. The second action is that of an organic acid (salt). It is considered that the organic acid (salt) becomes the core of the bubble growth points, so that the number of bubble growth points becomes fine and large.

Organic acids (salts) are highly hydrophilic compounds. However, since the polyolefin-based resin used as the matrix is hydrophobic, it is considered that the organic acid (salt) exists in a state of being aggregated to some extent in the melted polyolefin-based resin (that is, in the resin composition). It is assumed that the aggregated portion of this organic acid (salt) is the core of the bubble growth point. From these facts, it is considered that when the aggregated portion of the organic acid (salt) becomes large, the nucleus of the bubble growth point also becomes large, and as a result, the bubble diameter of the obtained foam becomes large.

It is considered that a compound having an amino group such as HALS has a high affinity with an acidic compound. Here, consider the case where the amino group contained in HALS is a tertiary amino group. In this case, HALS has a weak interaction with the organic acid (salt). Therefore, HALS does not affect the aggregated form of the organic acid (salt), and it is considered that the aggregated portion of the organic acid (salt) is absent or small. As a result, HALS is considered to have no effect on the formation of bubble growth points.

On the other hand, consider the case where the amino group contained in HALS is a secondary amino group. In this case, HALS becomes more basic and has a strong interaction with the organic acid (salt). Therefore, HALS acts on the aggregated form of organic acids (salts). When the amino group contained in HALS is a secondary amino group and the molecular weight of HALS is small, it is considered that the HALS does not have an effect enough to change the aggregation form of the organic acid (salt). On the other hand, when the amino group contained in HALS is a secondary amino group, the molecular weight of HALS is large, and two or more secondary amino groups are contained in one molecule, the HALS is an organic acid (salt). ) Is likely to be further aggregated, and it is considered that the nucleus of the bubble growth point is enlarged. As a result, it is presumed that the bubble diameter of the obtained foam becomes large even if the bubble nucleation agent is added. From the above inference, in order to obtain a foam having a fine bubble diameter, HALS needs to satisfy any of the above conditions (a) to (c).

The weight average molecular weight of the hindered amine-based light stabilizer under the above condition (b) is preferably 1200 or less, more preferably 1000 or less, still more preferably 800 or less, because the effect of suppressing coarsening of the bubble diameter is high.

The weight average molecular weight of the hindered amine-based light stabilizer under the above condition (c) is preferably 1800 or more, more preferably 2000 or more, because it is excellent in long-term weather resistance.

Under the above conditions (a) and (b), the content of the hindered amine-based light stabilizer is preferably 0.005 parts by weight or more, more preferably 0.010 parts by weight or more, based on 100 parts by weight of the polyolefin-based resin. , 0.020 parts by weight or more is more preferable. Under the above conditions (a) and (b), the content of the hindered amine-based light stabilizer is preferably 2.000 parts by weight or less, more preferably 1.000 parts by weight or less, based on 100 parts by weight of the polyolefin-based resin. , 0.600 parts by weight or less is more preferable. According to this configuration, there is an advantage that the balance between weather resistance and contamination by bleeding on the surface of HALS is excellent.

Under the above condition (c), the content of the hindered amine-based light stabilizer is preferably 0.005 parts by weight or more, more preferably 0.010 parts by weight or more, and 0.020 parts by weight, based on 100 parts by weight of the polyolefin-based resin. More than parts by weight is more preferable. Under the above condition (c), the content of the hindered amine-based light stabilizer is preferably 0.120 parts by weight or less, more preferably 0.100 parts by weight or less, and 0.090 parts by weight, based on 100 parts by weight of the polyolefin-based resin. It is more preferably parts by weight or less. According to this configuration, it has the advantages of being excellent in the effect of suppressing coarsening of the bubble diameter and being excellent in weather resistance.

HALS that does not contain or contains one secondary amino group in one molecule includes Tinuvin622 SF (manufactured by BASF), TinuvinPA123 (manufactured by BASF), TinuvinPA144 (manufactured by BASF), LA-52 (manufactured by BASF) as commercially available products. ADEKA), LA-81 (ADEKA), LA-40MP (ADEKA) and the like.

Examples of HALS having a weight average molecular weight of 1,500 or less include Tinuvin 770 DF (manufactured by BASF) and Uvinul 4050FF as commercially available products.

Examples of HALS containing two or more secondary amino groups in one molecule and having a weight average molecular weight of more than 1,500 include Chimassorb 944FDL (manufactured by BASF) and Chimassorb 2020FDL (manufactured by BASF) as commercially available products. ..

HALS can be used in the form of liquid, powder, granules, pellets and the like. HALS can also be used as a composition (so-called masterbatch) in which HALS is mixed in a high concentration in advance with components such as a resin and a resin additive.

[Weather resistant agents other than hindered amine light stabilizers (HALS)]
As one embodiment of the present invention, other weatherproofing agents may be used in combination with the use of HALS. In other words, the foam may further contain a weather resistant agent other than HALS in addition to HALS. As the weather resistant agent other than HALS, a weather resistant agent usually used for polyolefin resin non-crosslinked extruded foam can be used, and for example, an ultraviolet absorber (hereinafter, also referred to as UVA), an ultraviolet shielding agent such as carbon black, etc. , Quenching agents such as organic nickel compounds and the like. It is preferable to use an ultraviolet absorber (UVA) in combination with HALS because a small amount has a large effect of improving the weather resistance of the foam.

Examples of UVA include triazine-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzoate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers.

The melting point of UVA is preferably 160 ° C. or lower, more preferably 150 ° C. or lower, and even more preferably 145 ° C. or lower, because uniform bubble formation is performed. When the melting point of UVA is 160 ° C. or lower, the resin composition is difficult to solidify even when the resin temperature at the time of extrusion is lowered, and the generation of agglomerates in the resin composition can be suppressed. As a result, it is easy to obtain a foam having a uniform cell diameter. The resin composition is intended to be a melt-kneaded product obtained by melt-kneading a raw material resin and other components at the time of producing a foam. The method for producing the foam is described in detail in the following [Method for producing the polyolefin-based resin non-crosslinked extruded foam].

UVA can be used in the form of liquid, powder, granules, pellets and the like. UVA can also be used as a composition (so-called masterbatch) in which UVA is mixed in a high concentration in advance with components such as a resin and a resin additive.

The amount of the weather resistant agent other than HALS added in the production of the present foam, in other words, the content of the weather resistant agent other than HALS in the present foam is 0.01 part by weight to 3 parts by weight with respect to 100 parts by weight of the polyolefin resin. .00 parts by weight is preferable, 0.03 parts by weight to 1.00 parts by weight is more preferable, 0.04 parts by weight to 0.70 parts by weight is more preferable, and 0.05 parts by weight to 0.50 parts by weight is particularly preferable. preferable. When the addition amount (content) of the weather resistant agent other than HALS is 0.01 parts by weight or more, the weather resistance of the obtained foam is good. Further, when the addition amount (content) of the weather resistant agent other than HALS is 3.00 parts by weight or less, bleeding of the weather resistant agent other than HALS on the foam surface over time can be suppressed, and as a result, bleeding of the weather resistant agent other than HALS can be suppressed. , Transfer to buffer can be suppressed.

[Antioxidant]
In the production of the present foam, it is preferable to use an antioxidant in combination with HALS and a weathering agent other than HALS added as needed. In other words, the foam preferably contains an antioxidant in addition to HALS and, optionally, non-HALS weathering agents. According to this configuration, there is an advantage that the processing thermal stability of HALS and weather resistant agents other than HALS added (included) as needed is excellent. Examples of the antioxidant include a phenol-based antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant. These antioxidants may be used alone or in combination of two or more.

Examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol and tetrakis [methylene-3 (3', 5'-di-t-butyl-4-hydroxyphenyl) propionate]. Methan, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, 3,9-bis [2- {3- (3-t-butyl-4-hydroxy-5-methylphenyl) ) Propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5.5] undecane, 1,3,5-tris2 [3 (3,5-di-t-) Butyl-4-hydroxyphenyl) propionyloxy] ethyl isocyanate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris (3, 5-di-t-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-N-bis-3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate, 1,6 -Hexanediol bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2-thiobis-diethylenebis [3- (3,5-di-t-butyl-4-) Hydroxyphenyl) propionate], 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl-6-t-butylphenol), 2, 2'-methylene-bis- (4,6-di-t-butylphenol), 2,2'-ethylidene-bis- (4,6-di-t-butylphenol), 2,2'-butylidene-bis- (4,6-di-t-butylphenol) 4-Methyl-6-t-Butylphenol), 4,4'-Butylidenebis (3-Methyl-6-t-Butylphenol), 2-t-Butyl-6- (3-t-Butyl-2-Hydroxy-5-) Methylbenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl-6- (1- (3,5-di-t-amyl-2-hydroxyphenyl) ethyl) phenyl acrylate, tocopherols, etc. Can be mentioned. As the 2,2'-ethylidene-bis- (4,6-di-t-butylphenol), a commercially available product such as "Cheminox 1129" manufactured by Chemipro Kasei Co., Ltd. can also be used.

Examples of phosphorus-based antioxidants include tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearylpentaerythritol diphosphite, and bis (2,4-di-). t-Butylphenyl) pentaerythritol diphosphite, bis (2,4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) ) Pentaerythritol diphosphite, bis (2,4-dicumylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4'-diphenylenediphosphonite, 2, 2'-Methylenebis (4,6-di-t-butylphenyl) 2-ethylhexyl phosphite, 2,2'-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphite, bis (2,4) -Di-t-butyl-6-methylphenyl) ethylphosphite, 2- (2,4,6-tri-t-butylphenyl) -5-ethyl-5-butyl-1,3,2-oxaphosphorinane , 2,2', 2''-Nitrilo [triethyl-tris (3,3'5,5'-tetra-t-butyl-1,1'-biphenyl-2,2'-diyl) phosphite, 2, 4,8,10-Tetra-t-butyl-6- [3- (3-methyl-4-hydroxy-5-t-butylphenyl) propoxy] dibenzo [d, f] [1,3,2] dioxa Hosfepine and the like can be mentioned.

Examples of the sulfur-based antioxidant include dimethyl disulfide, diethyl disulfide, di-n-propyl disulfide, di-n-butyl disulfide, di-sec-butyl disulfide, di-t-butyl disulfide, and di-t-amyl disulfide. , Dicyclohexyl disulfide, di-t-octyl disulfide, di-n-dodecyl disulfide, di-t-dodecyl disulfide and the like.

Examples of the foaming agent that can be used in the production of the present foam include (a) aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane; and (b) cyclopentane, cyclobutane, and the like. Aliphatic hydrocarbons; (c) ethers such as dimethyl ether, diethyl ether, methyl ethyl ether; (d) alcohols such as methanol and ethanol; (e) inorganic gases such as air, nitrogen and carbon dioxide; and ( f) Water, etc. can be mentioned. One of these foaming agents may be used alone, or two or more of them may be used in combination. Among these, the foaming agent is preferably an aliphatic hydrocarbon because it is easy to obtain a desired foaming ratio, a desired closed cell ratio, and a desired average cell diameter, and normal butane and / or isobutane is particularly preferable. .. The amount of the foaming agent added is not particularly limited and may be appropriately adjusted because it varies depending on the type of the foaming agent and the target foaming ratio of the foam. In the production of the present foam, the amount of the foaming agent added is preferably 0.5 parts by weight to 20.0 parts by weight with respect to 100 parts by weight of the raw material resin component constituting the polyolefin-based resin non-crosslinked extruded foam. More preferably, it is from 0.0 parts by weight to 15.0 parts by weight.

In the production of the present foam, it is possible to add a bubble nucleation aid for the purpose of promoting the effect of the bubble nucleation agent. In other words, the foam preferably further contains a bubble nucleation aid. Examples of the bubble nucleation aid include talc, silica, calcium carbonate, zeolite, zinc oxide, and lithium compounds. Examples of the lithium compound include lithium acetate, lithium oxalate, lithium citrate, lithium carbonate, lithium borate, lithium stearate and the like. The bubble nucleation aid preferably contains a lithium compound, and more preferably lithium carbonate, because it has a high effect of reducing the bubble diameter when used in combination with the bubble nucleation agent. In the production of this foam, as the bubble nucleation aid, a powdery bubble nucleation aid may be directly used, or a masterbatch in consideration of mixing with the raw material resin component (main material) is used. You may.

In the production of this foam, if necessary, functional additives such as shrinkage inhibitors, crystal nucleating agents, heat stabilizers, antistatic agents, conductivity-imparting agents, flame retardants, lubricants, inorganic fillers, etc. Other additives such as colorants and pigments may be added. In other words, the present foam may contain the above-mentioned other additives as necessary.

Examples of the anti-shrinkage agent include glycerin monostearate.

In the production of the present foam, there is no limitation on the addition of the colorant. In the production of the present foam, a natural color foam can be obtained without adding a colorant, or a colorant such as blue, red, or black can be added to obtain a foam of a desired color. Examples of the colorant include perylene-based organic pigments, azo-based organic pigments, quinacridone-based organic pigments, phthalocyanine-based organic pigments, slene-based organic pigments, dioxazine-based organic pigments, isoindoline-based organic pigments, and carbon black.

[Manufacturing method of non-crosslinked extruded foam made of polyolefin resin]
The foam can be produced, for example, by sequentially performing the following operations (1) to (3): (1) the above-mentioned polyolefin resin, hindered amine light stabilizer and foaming agent, and, if necessary, the above-mentioned polyolefin resin, hindered amine light stabilizer and foaming agent. Melt-knead other additives such as bubble nucleating agent, weathering agent other than HALS, and shrinkage inhibitor; (2) extrude the obtained melt-kneaded product; (3) foam-mold the melt-kneaded product by the extrusion. To do. If necessary, other additives or the like may be used in an appropriate step for producing the present foam.

As a method for producing the present foam, any method may be used as long as a polyethylene-based resin non-crosslinked extruded foam can be obtained. In the method for producing the foam, a tandem extruder device in which a twin-screw extruder and a single-screw extruder are connected may be used. Specific examples of the method for producing the foam include the following operations (1) to (6) in order: (1) Raw material resin such as polyolefin resin and hindered amine light stabilizer. In addition, if necessary, prepare a predetermined amount of each of other additives such as a bubble nucleating agent, a weather resistant agent other than HALS, and a shrinkage inhibitor, and prepare all the prepared raw materials in the first extruder (first stage extruder). , Biaxial); (2) melt-knead the supplied raw materials at a temperature suitable for kneading; (3) the first extruder for the obtained melt-kneaded product (resin composition). The foaming agent is press-fitted in the middle of the above; (4) The obtained resin composition is adjusted to a desired discharge amount, and the second extruder connected from the first extruder (second-stage extruder, single extruder) is used. Discharge to the shaft); (5) Then, in the second extruder, adjust (for example, cool) the temperature of the discharged resin composition to a temperature suitable for foaming; (6) Adjust to a temperature suitable for foaming. The prepared resin composition is extruded from a die attached to the tip of the second extruder into a region of lower pressure than in the extruder to foam the resin composition.

In the above (1), the operation of supplying all the prepared raw materials to the first extruder will be specifically described. For all the prepared raw materials, each raw material may be supplied to the first extruder from a separate feeder, or a part or all of the raw materials may be supplied to the first extruder together. When each of the prepared raw materials is supplied to the first extruder from a separate feeder, each raw material may be supplied to the first extruder at the same time, or may be supplied at any time. When a part or all of the prepared raw materials are supplied to the first extruder together, a part or all of the prepared raw materials may be mixed in advance to form a mixture, and the mixture may be supplied to the first extruder.

The temperature suitable for the kneading may be a temperature at which the raw material resin is surely melted and the melted raw material resin is preferably kneaded with the hindered amine light stabilizer and the foaming agent. Not limited. In one embodiment of the present invention, the temperature suitable for the kneading is preferably a temperature equal to or higher than the melting point of the raw material resin (for example, a polyolefin resin). When the bubble nucleating agent is used in one embodiment of the present invention, the temperature suitable for the kneading is preferably a temperature at which the effect of the bubble nucleating agent used is efficiently exhibited. When the bubble nucleating agent contains a decomposing foaming agent, the temperature at which the effect of the bubble nucleating agent is efficiently exhibited is the temperature at which the decomposition of the decomposing foaming agent proceeds sufficiently and the desired nucleation action is obtained. Is. For example, when a mixture of sodium hydrogen carbonate and monosodium citrate is used as the bubble nucleating agent, the temperature suitable for the kneading is a temperature at which the effect of the bubble nucleating agent is efficiently exhibited 180. ° C to 230 ° C is preferable.

The temperature suitable for foaming is not particularly limited. The temperature suitable for foaming is generally preferably in the range of -10 ° C to + 20 ° C with respect to the melting point of the polyolefin resin as the main raw material, which is the temperature of the resin composition extruded from the die.

By selecting a die to be attached to the tip of the second-stage extruder according to the shape of the desired foam, it is possible to manufacture extruded foams of various shapes such as flat foams and round bar foams. it can. The extruding conditions of the resin composition, the taking-back conditions of the extruded foam, the cooling conditions of the extruded foam, and the like may be appropriately set. The present foam is preferably a flat foam, in other words, a foam plate.

The region having a lower pressure than that in the extruder is preferably a region under atmospheric pressure. In other words, the inside of the extruder is preferably higher than atmospheric pressure.

[Polyolefin-based resin non-crosslinked extruded foam]
The foaming ratio of the present foam is preferably 3.0 to 35.0 times. According to this configuration, the processability of the foam for making it into a cushioning material, which is one of the main uses of the foam, is improved. As a result, the obtained foam can be processed into a cushioning material, which can be used as a cushioning material for a wide range of transported products from lightweight parts to heavy parts. The foaming ratio of the foam is not particularly limited and may be appropriately selected depending on the weight of the product. The lower limit of the foaming ratio of (a) the foam is more preferably 5.0 times or more, further preferably 6.0 times or more, because it is excellent in the balance of lightness, grip of the product, cushioning property and the like. b) The upper limit of the foaming ratio of the foam is more preferably 30.0 times or less, further preferably 28.0 times or less. The foaming ratio of the foam may be 3.0 to 30.0 times, 3.0 to 28.0 times, or 5.0 to 35.0 times. It may be 5.0 times to 30.0 times, 5.0 times to 28.0 times, 6.0 times to 35.0 times, 6.0 times. It may be double to 30.0 times, or 6.0 times to 28.0 times. In the present specification, the foaming ratio of the foam is a value obtained by the measuring method described in Examples described later.

The thickness of the foam is preferably 20 mm or more, more preferably 30 mm or more, and even more preferably 40 mm or more. According to this configuration, (a) the advantage of being able to process the foam into various cushioning material shapes, and the fact that it can be used as a cushioning material in a single piece (that is, in one foam) instead of a laminated sheet. Therefore, it has an advantage that a homogeneous material can be easily obtained as a cushioning material. The upper limit of the thickness of the foam is not particularly limited. The upper limit of the thickness of the foam is preferably 160 mm or less, more preferably 100 mm or less, still more preferably 70 mm or less because it is easy to secure the thickness by extrusion foaming. The thickness of the foam is preferably 20 mm to 160 mm, preferably 30 mm to 160 mm, 40 mm to 160 mm, 20 mm to 100 mm, 30 mm to 100 mm, and 40 mm. It may be ~ 100 mm, 20 mm to 70 mm, 30 mm to 70 mm, or 40 mm to 70 mm.

This foam can achieve both a fine cell diameter and a high closed cell ratio. The average cell diameter of the present foam is preferably 100 μm or more, more preferably 150 μm or more, still more preferably 180 μm or more, because it is easy to adjust to a desired closed cell ratio and foaming ratio. In the cushioning material application, which is the main application of the foam, the average cell diameter of the present foam is preferably 600 μm or less, more preferably 500 μm or less, still more preferably 400 μm or less, because it is excellent in product protection. The average cell diameter of the foam is preferably 100 μm to 600 μm, may be 100 μm to 500 μm, may be 100 μm to 400 μm, may be 150 μm to 600 μm, or may be 150 μm to 500 μm. , 150 μm to 400 μm, 180 μm to 600 μm, 180 μm to 500 μm, 180 μm to 400 μm. In the present specification, the average cell diameter of the foam is a value obtained by the measuring method described in Examples described later.

The closed cell ratio of this foam is preferably 70% or more, more preferably 75% or more, and more preferably 80%, because the cushioning performance as a cushioning material, the repetitive use performance, and the dimensional recovery during punching are improved. The above is more preferable.

This foam has excellent weather resistance. As used herein, having excellent weather resistance is intended to mean that there is no significant increase in the amount of wear even after outdoor exposure as compared to before outdoor exposure.

For this foam, the value (B / A) obtained by dividing the wear amount (B) of the foam subjected to the outdoor exposure test by the wear amount (A) of the foam not subjected to the outdoor exposure test is less than 4.00. Is more preferable, less than 3.50 is more preferable, less than 3.00 is more preferable, less than 2.50 is more preferable, less than 2.00 is more preferable, less than 1.50 is further preferable, and less than 1.10 is particularly preferable. ..

Here, the outdoor exposure test is carried out for one year according to the method A described in JIS K 7219. The amount of wear of the foam is the amount of change in weight (mg) of the foam before and after the wear test. The wear test is carried out using a foam and a particle size P150 polishing cloth (JIS R 6251 certified product) under the conditions of a load of 1 kg, a speed of 2000 mm / min, a moving distance of 10 mm, and a number of reciprocations of 1000 times. The test methods of the outdoor exposure test and the abrasion test will be described in detail in the following examples.

[3. Cushioning material]
The cushioning material according to the embodiment of the present invention is described in the above [2. Polyolefin-based resin non-crosslinked extruded foam] The polyolefin-based resin non-crosslinked extruded foam according to the section. By appropriately processing the foam, it can be used as a cushioning material according to an embodiment of the present invention. The cushioning material according to the embodiment of the present invention can be used as a cushioning packaging material suitable for transporting various members, and can be particularly preferably used as a cushioning material for heavy parts. In addition, the cushioning material according to the embodiment of the present invention can be suitably used as a cushioning packaging material for articles such as glass that are easily damaged and have sharp surfaces (corners).

The processing method and means of the foam are not particularly limited. Examples of the processing method and means include (a) cutting with a slicer, (b) punching with a Thomson blade, and (c) thermal bonding with a hot dryer.

Hereinafter, an embodiment of the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

The raw materials used in the following examples and comparative examples are as follows.

[Polyolefin-based resin]
A-1: Branched low density polyethylene (LDPE) "C470" (manufactured by Ube Maruzen Polyethylene Co., Ltd., density 918 kg / m ³ , MFR 2.0 g / 10 minutes)
A-2: Ethylene / α-olefin copolymer "0540F" (manufactured by Ube Maruzen Polyethylene Co., Ltd., density 904 kg / m ³ , MFR 4.0 g / 10 minutes)
A-3: Isoprene-modified polypropylene resin (ethylene content 3%, MFR 4.5 g / 10 minutes, melting point 145 ° C)
Here, the isoprene-modified polypropylene-based resin was produced as follows. 1.1 parts by weight of t-butylperoxyisopropyl carbonate as a radical polymerization initiator with respect to 100 parts by weight of polypropylene / ethylene random copolymer (ethylene content 3%, MFR 8.0 g / 10 minutes, melting point 144 ° C.). And 0.5 part by weight of isoprene monomer as a conjugated diene compound was used to modify the polypropylene / ethylene random copolymer.

[Bubble nucleation agent]
B-1: Sodium hydrogen carbonate (pyrolytic foaming agent)
B-2: Monosodium citrate (organic acid salt)
[Anti-shrinkage agent]
C-1: Glycerin monostearate "Rikemar S100P" (manufactured by RIKEN Vitamin Co., Ltd.)
[Hindered Amin-based Light Stabilizer (HALS)]
D-1: High molecular weight HALS "Tinuvin622SF" (manufactured by BASF, weight average molecular weight 6800, melting point 55 ° C. to 70 ° C., number of secondary amino groups in one molecule: 0)
D-2: Low molecular weight HALS "Tinuvin 770DF" (manufactured by BASF, weight average molecular weight 490, melting point 81 ° C to 85 ° C, number of secondary amino groups in one molecule: 2)
D-3: High molecular weight HALS "Chimassorb 944FDL" (manufactured by BASF, weight average molecular weight 7200, melting point 100 ° C to 135 ° C, number of secondary amino groups in one molecule: 2 or more)
D-4: High molecular weight HALS "Chimassorb 2020FDL" (manufactured by BASF, weight average molecular weight 5900, melting point 120 ° C to 150 ° C, number of secondary amino groups in one molecule: 2 or more)
[Weather resistant agents other than HALS]
E-1: Benzotriazole UVA "Tinuvin 326" (manufactured by BASF, melting point 137 ° C to 141 ° C)
E-2: Benzophenone UVA "Chimassorb81" (manufactured by BASF, melting point 45 ° C to 48 ° C)
E-3: Benzoate-based UVA "Tinuvin 120" (manufactured by BASF, melting point 192 ° C to 197 ° C).

(Examples 1 to 11 and Comparative Examples 1 to 6)
Each of the polyolefin resin, the bubble nucleating agent, the shrinkage inhibitor, HALS and the weather resistant agent other than HALS was prepared in the blending amounts shown in Tables 1 and 2. The prepared raw material was supplied to the first extruder of the tandem extruder apparatus. Here, as the tandem extruder device, a tandem extruder device in which a twin-screw extruder having a shaft diameter of 40 mm is connected as the first extruder and a single-screw extruder having a shaft diameter of 90 mm is connected as the second extruder is used. .. The first extruder was set to 220 ° C., i.e. the temperature of melt kneading was 220 ° C. After melt-kneading the raw materials supplied to the first extruder, 3.5 parts by weight of isobutane as a foaming agent was press-fitted into the melt-kneaded product (resin composition) from the middle of the first extruder. Was mixed. The obtained resin composition was discharged from the first extruder to the second extruder (diameter 90 mm). Then, for (i) Examples 1 to 10 and Comparative Examples 1 to 4, the discharged resin composition was cooled to 108 ° C. in the second extruder, and (ii) for Examples 11 and Comparative Examples 5 to 6. , The discharged resin composition was cooled to 145 ° C. in the second extruder. Then, the cooled resin composition was extruded from a die attached to the tip of the second extruder under atmospheric pressure at a discharge rate of 40 kg / h to foam the resin composition. Here, the die attached to the tip of the second extruder had a rectangular shape, and the size of the opening was 50 mm × 5.5 mm. Further, the inside of the extruder was higher than the atmospheric pressure, that is, the area under the atmospheric pressure was a region of lower pressure than the inside of the extruder. The foam extruded from the die was taken up by a take-up machine and molded into a plate shape having a width of 130 mm and a thickness of 45 mm by a molding die to obtain a foam. The obtained foam had no voids and had a high closed cell ratio.

The following physical property evaluations were carried out for each of the foams of Examples 1 to 11 and Comparative Examples 1 to 6 thus obtained. The evaluation results are shown in Table 1. The test methods and judgment criteria used for various evaluation methods are as follows.

[Melt Mass Flow Rate (MFR)]
The MFR of each polyethylene resin (A-1 and A-2) was measured at a test temperature of 190 ° C. and a test load of 2.16 kg according to JIS K-7210.

The MFR of the polypropylene resin (A-3) was measured according to JIS K-7210 at a test temperature of 230 ° C. and a test load of 2.16 kg.

[Melting point]
The melting point of the polypropylene resin of A-3 was measured by the DSC method. The specific operation procedure is as follows: (1) 5 to 6 mg of polyethylene resin or 5 to 6 mg of polypropylene resin is heated from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min to melt it. After; (2) After lowering the temperature from 220 ° C. to 40 ° C. at a temperature lowering rate of 10 ° C./min for crystallization; (3) Further raising the temperature from 40 ° C. to 220 ° C. at a heating rate of 10 ° C./min. did. The temperature of the peak (melting peak) of the DSC curve obtained at the time of the second temperature rise (that is, at the time of (3)) was defined as the melting point.

[Weight average molecular weight of HALS]
As the GPC apparatus, Water2695 manufactured by Waters was used. The detector used was RI-8020 manufactured by Tosoh, the guard column used was TSKgelα manufactured by Tosoh, and the analysis column used was TSKgelα-M + TSKgelα-2500 manufactured by Tosoh. The column temperature was set to 40 ° C. As the eluent, 100 mM LiBr and 30 mM phosphoric acid-containing DMF were used, and the eluate flow rate was 0.5 ml / min. About 30 mg of each HALS was weighed and weighed. 10 ml of the eluent was added to the weighed HALS to dissolve the HALS, and then the solution was passed through a PTFE disposable filter having a pore size of 0.45 μm to prepare a sample. 100 μl of the sample was injected into the GPC apparatus. From the obtained chromatogram, the polystyrene-equivalent weight average molecular weight was calculated using Waters analysis software Emper3. As a standard sample, STANDERD polystyrene SM-105 (molecular weight: 3.73E + 06, 2.48E + 06, 6.66E + 05, 2.88E + 05, 5.51E + 04, 2.86E + 04, 1.30E + 04, 2.94E + 03, 1.28E + 03) and polystyrene Mp370 (molecular weight: 3.70E + 02) manufactured by Agilent Technologies were used.

[Closed cell ratio]
From the central portion in the thickness direction and the width direction of each of the foams obtained in Examples and Comparative Examples, the width is 20 mm, the thickness is 20 mm, and the length is 20 mm so as not to include the surface layer portion (which can be said to be both end faces in the thickness direction). A 30 mm test piece was cut out. Here, the thickness direction of the foam can be said to be the short direction in the cross section perpendicular to the extrusion direction of the foam, and the width direction of the foam can be said to be the longitudinal direction in the cross section perpendicular to the extrusion direction of the foam. .. ^{Using the test piece, the volume Vc (cm 3} ) of the test piece was measured using an air pycnometer (air comparative hydrometer model 1000 manufactured by Tokyo Science Co., Ltd.) in accordance with the method described in ASTM D2856. Next, the same test piece after the measurement was submerged in ethanol in a measuring cylinder containing ethanol. ^{The apparent volume Va (cm 3} ) was determined from the amount of increase in the liquid level (ethanol level) of the graduated cylinder (also called the submersion method). The closed cell ratio (%) was calculated according to the following formula:
Closed cell ratio (%) = (Vc / Va) x 100
The measurement was carried out for three test pieces per foam, and the average value was taken as the closed cell ratio of the foam.

[Effervescence magnification]
The foam density was determined by the following formula using the weight W (g) of the test piece used in the measurement of the closed cell ratio and the volume Va (cm ^{3) determined by the submersion method.}
Foam density (g / cm ³ ) = W / Va.

Moreover, the resin density was measured according to JIS K-7112. Using the above foam density (g / cm ³ ) and resin density (g / cm ³ ), the foaming ratio was calculated by the following formula:
Foaming magnification (times) = resin density / foam density.

[Average cell diameter]
For the foams obtained in Examples and Comparative Examples, the direction perpendicular to both the extrusion direction (MD) and the thickness direction (ZD) was defined as the width direction (TD). For the foam, the surface perpendicular to the thickness direction was designated as the surface A, the surface perpendicular to the extrusion direction was designated as the surface B, and the surface perpendicular to the width direction was designated as the surface C. The foams obtained in Examples and Comparative Examples were cut along the surface B to prepare three samples A having a length in the extrusion direction (MD) of 20 mm. In sample A, the planes parallel to each of the above-mentioned planes A, B and C were designated as planes A1, B1 and C1. Further, from each sample A, a cube sample B having a side of 5 to 10 mm was cut out for each measurement point (5 points) shown below. Here, the sample B was prepared (cut out) using a double-edged razor [Feather-made, high-stainless steel double-edged], taking great care not to destroy the bubble film (cell film). In sample B, among the surfaces parallel to each of the above-mentioned surfaces A, B, and C, the cut surfaces cut by using a double-edged razor were designated as surfaces A2, B2, and C2. When there are two cut surfaces, one of them is designated as surfaces A2, B2 and C2. For sample B, surfaces A2, B2 and C2 were observed with a microscope [VHX-900, manufactured by KEYENCE CORPORATION], and images of each surface were obtained. In each of the obtained images, a line segment having a length of 4000 μm was drawn, the number of bubbles n through which the line segment passed was measured, and the bubble diameter was calculated by the following formula.

Bubble diameter (μm) = 4000 / n
For the three samples A, the arithmetic mean value of the bubble diameters obtained from the images of the surfaces A2, B2, and C2 of the sample B at each measurement point (5 points) was defined as the average cell diameter (μm). That is, the arithmetic mean value of the bubble diameters of 45 surfaces (3 surfaces × 5 locations × 3 samples A) was defined as the average cell diameter (μm).

The measurement points will be described with respect to surface A. As shown below, 5 points were measured with respect to the surface A.
・ Central part in the width direction and thickness direction (1 point, "Measurement point A")
-The central part of the measurement point A and the end part in the width direction in the center part in the thickness direction (two points for both ends in the width direction)
-The central part between the measurement point A and the end part in the thickness direction in the center part in the width direction (two points for both ends in the thickness direction)
[thickness]
For the sample A (3 pieces) collected for measurement with the above [average cell diameter], a total of 3 points were measured, 30 mm inside from each of the central portion in the width direction and both ends in the width direction. The average value of the three places was taken as the thickness per sample A, and the average value of three samples A was taken as the thickness of the foam.

[Weatherability]
The weather resistance was judged by the abrasion resistance evaluation before and after the outdoor exposure test of the foam. First, two test pieces were cut out from the central portion in the thickness direction of the foams obtained in Examples and Comparative Examples with dimensions of MD: 200 mm, TD: 80 mm, and ZD: 10 mm so as not to include the surface layer portion. .. Using one of the two test pieces, an outdoor exposure test was conducted for one year according to the method A described in JIS K 7219.

Abrasion resistance evaluation was performed on the test pieces that were subjected to the outdoor exposure test and the test pieces that were not subjected to the outdoor exposure test. Each test piece was fixed to a surface tester (HEIDON TYPE-14, manufactured by Shinto Kagaku Co., Ltd.). A jig with a width of 13 mm, a length of 60 mm, and a thickness of 3.5 mm is set on the ASTM flat surface indenter set in the testing machine, and a particle size P150 polishing cloth (JIS R 6251 certified) is set on the surface of the jig in contact with the foam. Product) was pasted. Using these test pieces and a testing machine, a wear test was performed under the conditions of a load of 1 kg, a speed of 2000 mm / min, a moving distance of 10 mm, and a number of reciprocations of 1000 times. The change in the weight of the sample before and after the wear test was defined as the amount of wear (mg), and the wear resistance was evaluated. The smaller the amount of wear, the better the wear resistance.

The weather resistance was evaluated by a value (B / A) obtained by dividing the wear amount (B) of the test piece subjected to the outdoor exposure test by the wear amount (A) of the test piece not subjected to the outdoor exposure test.
Weather resistance was judged by the following criteria:
◎ (Very good): Less than 1.10 ○ (Good): 1.10 or more, less than 1.50 △ (Pass): 1.50 or more and less than 4.00 × (Bad): 4.00 or more

As shown in Table 1, Examples 1 to 11 had a small bubble diameter and excellent weather resistance.

As shown in Table 1, in Comparative Example 1, the added HALS did not satisfy the condition (c). Specifically, the HALS added in Comparative Example 1 contains two or more secondary amino groups in one molecule, and the weight average molecular weight of the hindered amine-based light stabilizer is more than 1,500, but the amount of HALS added. Since the (content) was an addition amount exceeding the condition (c), the bubble diameter of the obtained foam was coarse.

In Comparative Example 2, the HALS added in the same manner as in Comparative Example 1 did not satisfy the condition (c). Specifically, the HALS added in Comparative Example 2 contains two or more secondary amino groups in one molecule, and the weight average molecular weight of the hindered amine-based light stabilizer is more than 1,500, but the amount of HALS added. Since the (content) was an addition amount exceeding the condition (c), the bubble diameter of the obtained foam was coarse.

In Comparative Example 3, since no weather resistant agent (weather resistant agent other than HALS and HASL) was added, the wear resistance after 1 year of outdoor exposure was significantly deteriorated, and the weather resistance was not satisfied. It was.

In Comparative Example 4, although a weather resistant agent other than HASL was contained, HALS was not added. As a result, the wear resistance one year after outdoor exposure was significantly deteriorated, and the weather resistance was not satisfied.

In Comparative Example 5, a foam was produced using the polyolefin resin used as isoprene-modified polypropylene. In Comparative Example 5, the HALS added in the same manner as in Comparative Example 1 did not satisfy the condition (c). Specifically, the HALS added in Comparative Example 5 contains two or more secondary amino groups in one molecule, and the weight average molecular weight of the hindered amine-based light stabilizer is more than 1,500, but the amount of HALS added. Since the (content) was an addition amount exceeding the condition (c), the bubble diameter of the obtained foam was coarse. Moreover, the weather resistance was not satisfactory.

In Comparative Example 6, since the weather resistant agent was not added, the abrasion resistance after 1 year of outdoor exposure was very deteriorated, and the weather resistance was not satisfied.

As described above, according to one embodiment of the present invention, (a) the bubble diameter is small, (b) it has excellent weather resistance, and (c) there is a risk of contamination, especially even after being stored outdoors. It is possible to provide a polyolefin-based resin non-crosslinked extruded foam and a cushioning material, which are less likely to be contaminated, (d) excellent in cost, production efficiency, recyclability and heat-sealing property, and (e) good in processability. Therefore, one embodiment of the present invention is suitable for a cushioning material for transporting key parts of an automobile whose contamination may lead to a serious defect, a cushioning material attached to a large trolley that can be stored outdoors, and the like. Available.

Claims (7)

It contains a polyolefin resin, a bubble nucleating agent containing a pyrolysis foaming agent and an organic acid (salt), and a hindered amine light stabilizer that satisfies any of the following conditions (a) to (c).
Polyolefin resin non-crosslinked extruded foam having a foaming ratio of 3 times or more:
Condition (a): The hindered amine-based light stabilizer does not contain or contains one secondary amino group in one molecule, and the content of the hindered amine-based light stabilizer is 100 parts by weight of the polyolefin-based resin. On the other hand, it is 0.001 part by weight to 3.000 parts by weight;
Condition (b): The weight average molecular weight of the hindered amine light stabilizer is 1,500 or less, and the content of the hindered amine light stabilizer is 0.001 weight by weight based on 100 parts by weight of the polyolefin resin. Parts to 3.000 parts by weight;
Condition (c): The hindered amine-based photostabilizer contains two or more secondary amino groups in one molecule, the weight average molecular weight of the hindered amine-based light stabilizer is more than 1,500, and the hindered amine-based photostabilizer is photostable. The content of the agent is 0.001 part by weight to 0.150 part by weight with respect to 100 parts by weight of the polyolefin resin. The polyolefin-based resin non-crosslinked extruded foam according to claim 1, wherein the polyolefin-based resin non-crosslinked extruded foam has an average cell diameter of 100 μm to 600 μm. The polyolefin-based resin non-crosslinked extruded foam according to claim 1 or 2, wherein the polyolefin-based resin non-crosslinked extruded foam has a thickness of 20 to 160 mm. The polyolefin-based resin non-crosslinked extruded foam according to any one of claims 1 to 3, wherein the polyolefin-based resin contains a polyethylene-based resin. The polyolefin-based resin non-crosslinked extruded foam according to claim 4, wherein the polyethylene-based resin contains 50% by weight or more of branched low-density polyethylene in 100% by weight of the polyethylene-based resin. The polyolefin-based resin non-crosslinked extruded foam according to any one of claims 1 to 5, wherein the closed-cell ratio of the polyolefin-based resin non-crosslinked extruded foam is 70% or more. A cushioning material containing the polyolefin-based resin non-crosslinked extruded foam according to any one of claims 1 to 6.