JP2020097689A - Foam board of extruded non-crosslinked polyethylene-based resin and method for producing the same - Google Patents

Abstract

To obtain a foam of extruded non-crosslinked polyethylene-based resin which has a fine cell diameter, a high closed cell ratio, and a large cross-sectional area, and is excellent in weather resistance.SOLUTION: A foam board of extruded non-crosslinked polyethylene-based resin having an expansion ratio of 5 times or more and 30 times or less and a thickness of 20 mm or more is provided that is obtained by performing extrusion foaming on a polyethylene-based resin composition including a foam nucleus-forming agent composed of a thermal decomposition type foaming agent and a citrate, a shrink-proof agent and a weather-proof agent, the weather-proof agent being included in an amount of 0.01 pts.wt. or more and 3 pts.wt. or less with respect to 100 pts.wt. of a raw material resin component, wherein a ratio B/A of an addition amount B of the shrink-proof agent to an addition amount A of the foam nucleus-forming agent is 0.3 or more and 4.0 or less.SELECTED DRAWING: None

Description

The present invention relates to a non-crosslinked polyethylene-based resin extruded foam board and a method for producing the same, and more particularly to a plate-shaped non-crosslinked polyethylene-based resin extruded foam having desired characteristics and cross-sectional shape by extrusion foaming.

Polyethylene resin foams are widely used as cushioning packaging materials because they are relatively excellent in flexibility and abrasion resistance. Polyethylene-based resin foams include bead foams, crosslinked batch foams, non-crosslinked extruded foams, etc., depending on their production methods.

Although some bead foams have excellent abrasion resistance, there is a concern that the beads may fall off, and therefore their use 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, an industrial heat insulating material, sports equipment and the like. However, since an extra step is required for cross-linking, the manufacturing cost becomes high, and the cross-linked foam cannot be returned to the original resin and reused, which makes it difficult for the current recycling society. It is not suitable. Further, it has a disadvantage that it is inferior in heat fusion property as compared with non-crosslinked polyethylene and thus has poor workability.

On the other hand, the non-crosslinked polyethylene-based resin foam produced by the extrusion method has many merits from the viewpoint that there is no possibility of bead loss and recycling and heat fusion are also possible. Non-crosslinked extruded foams using branched low-density polyethylene have been put to practical use. In particular, polyethylene-based resin extruded foam sheets can be thermoformed, so they are widely used as cushioning materials, packaging materials, containers, etc. ing. For example, Patent Document 1 discloses a non-crosslinked polyethylene resin extruded foam sheet having a dense and uniform cell diameter by using an organic decomposition type foaming agent as a cell nucleating agent as a cell nucleating agent. ..

However, the plate-shaped non-crosslinked polyethylene-based resin extruded foam with a large thickness is difficult to maintain a fine cell diameter and a high closed cell ratio because of the characteristics of the manufacturing method, so generally only those having a large cell diameter are distributed. In some fields, there is a tendency to be shunned because bubbles have a harder feel than fine ones and a bubble pattern is transferred. For example, Patent Document 2 relates to a non-crosslinked polyethylene resin extruded foam having a sufficient thickness and a high open cell ratio, but a plate-like foam having a large thickness has a large cell diameter. Alternatively, there is a tendency that the closed cell rate becomes low. A thick plate-like non-crosslinked polyethylene-based resin extruded foam having a small cell diameter and a high closed cell ratio is desired in order to have a buffering property capable of withstanding long-term use even for heavy articles. Further, as a market need, it is also desired to have weather resistance as a cushioning packaging material in order to prevent deterioration due to long-term use and storage.

JP, 2007-246776, A JP-A-2002-47369

Therefore, an object of the present invention is to use a non-crosslinked polyethylene-based resin extruded foam having a large cell diameter, a small cell diameter, a high closed cell ratio, weather resistance, and a large cross-sectional area, which is preferably used as a cushioning material. It's easy to get.

The present inventor, as a result of intensive studies in view of the above problems, discovered that the addition of a weathering agent to impart weather resistance tends to increase the cell diameter of the resulting foam. Therefore, as a result of further intensive studies, by adjusting the addition amount ratio of the cell nucleating agent of the specific component and the shrinkage inhibitor, the cell diameter is fine and the closed cell is high while having weather resistance. Has succeeded in producing a foam having a high rate, and has completed the present invention.

That is, the first aspect of the present invention comprises, based on 100 parts of a polyethylene resin, a cell nucleating agent consisting of a thermal decomposition type foaming agent and a citrate, a shrinkage inhibitor, and a weathering agent. Contains 0.01 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the raw material resin component, and the ratio B/A of the addition amount B of the shrinkage inhibitor to the addition amount A of the cell nucleus forming agent is 0.3. A non-crosslinked polyethylene resin extruded foam board satisfying the following (a) to (b) obtained by extruding and foaming a polyethylene resin composition having a ratio of 4.0 or more (the non-crosslinked polyethylene according to the first aspect of the present invention) The resin-based extruded foam board and the non-crosslinked polyethylene-based resin extruded foam board according to the second aspect of the present invention may be referred to as the “non-crosslinked polyethylene-based resin extruded foam board of the present invention”.
(A) The expansion ratio is 5 times or more and 30 times or less.
(D) The thickness is 20 mm or more.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, it is preferable that the thermal decomposition type foaming agent is sodium hydrogen carbonate.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, it is preferable that the shrinkage inhibitor contains a fatty acid ester.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, it is preferable that the shrinkage inhibitor contains monoglyceride stearate.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, it is preferable that the polyethylene resin composition further contains a cell nucleation auxiliary agent.

In the non-crosslinked polyethylene-based resin extruded foam board of the present invention, it is preferable that the cell nucleation auxiliary agent contains a lithium compound.

In the non-crosslinked polyethylene-based resin extruded foam board of the present invention, the average cell diameter of the non-crosslinked polyethylene-based resin extruded foam board is preferably 100 μm or more and 600 μm or less.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, it is preferable that the non-crosslinked polyethylene resin extruded foam board has a closed cell ratio of 70% or more.

The second invention is obtained by melt-kneading in a extruder with a polyethylene resin, a cell nucleating agent consisting of a pyrolytic foaming agent and a citrate, a shrinkage inhibitor, a weathering agent, and a foaming agent. A method for producing a non-crosslinked polyethylene resin extruded foam board by extruding an expandable polyethylene resin composition obtained from a die attached to the tip of an extruder, wherein the shrinkage prevention is performed with respect to the addition amount A of the cell nucleating agent. The ratio B/A of the additive amount B of the agent is 0.3 or more and 4.0 or less, the weather resistance agent is 0.01 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the raw material resin component, and the foaming is performed. The present invention relates to a method for producing a non-crosslinked polyethylene resin extruded foaming board, which comprises extruding and foaming a water-soluble polyethylene resin composition under conditions such that a molding coefficient α represented by the following formula (1) is 1.5 or more.
Forming factor α=A _F /((Q/3600)/ρ _F ) ^(2/3)・・・Equation (1)
(In the above formula (1), A _F represents the cross-sectional area (m ² ) of the non-crosslinked polyethylene resin extruded foam board, Q represents the discharge amount (kg/hr) during extrusion foaming, and ρ _F is The density (Kg/m ³ ) of the non-crosslinked polyethylene resin extruded foam board is shown.)

According to the present invention, it is possible to easily obtain a board-like foam having a relatively large cross-sectional area, which has both a fine cell diameter and a high closed cell rate and has weather resistance.

The non-crosslinked polyethylene-based resin extruded foam board of the present invention is an extrusion using a polyethylene-based resin composition containing a cell nucleating agent which is a mixture of a thermal decomposition type foaming agent and citrate, a shrinkage inhibitor, and a weathering agent. It is a foam.

The non-crosslinked polyethylene resin extruded foam board of the present invention contains a polyethylene resin as a raw material resin component constituting the non-crosslinked polyethylene resin extruded foam board. Examples of the polyethylene-based resin include resins having an ethylene component unit of 50 mol% or more. High-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer. Coal, ethylene-propylene-butene-1 copolymer, ethylene-butene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-octene-1 copolymer An example is coalescence. Among these, it is preferable to use a low-density polyethylene having a branched structure as a main component from the viewpoint of excellent foamability, and it is particularly preferable to use a low-density polyethylene having a density of 935 kg/m ³ or less. The term “main component” of the low-density polyethylene-based resin means that the content of the low-density polyethylene-based resin is 60% by weight or more based on 100% by weight of the polyethylene-based resin. Further, the lower limit of the density of the low-density polyethylene-based resin is approximately 890 kg/m ³ . The preferred range of density of the low density polyethylene resin is ^{900kg / m 3 ~930kg / m 3} , preferably even at ^{910kg / m 3 ~925kg / m 3} , in particular 913kg ^{/ m 3} ~923kg ^/ m 3 Is preferred.

The polyethylene resin may be used alone or as a mixture of two or more kinds, or two or more kinds of the same resin having different densities may be mixed and used. Examples of a mixture of two or more polyethylene resins include low density polyethylene mixed with linear low density polyethylene.

The MFR of the polyethylene-based resin is preferably 0.05 to 15 g from the viewpoint that it has melt tension and can prevent excessive shear heat generation in the extruder and can easily set conditions suitable for extrusion foaming. /10 minutes, more preferably 0.5 to 10 g/10 minutes, further preferably 0.8 to 5.0 g/10 minutes, and particularly preferably 1.0 to 3.0 g/10 minutes.

In the non-crosslinked polyethylene resin extruded foam board of the present invention, a cell nucleating agent composed of a mixture of a pyrolytic foaming agent and a citrate is used. Examples of the thermal decomposition type foaming agent include ADCA (azodicarbonamide), DPT (N,N′-dinitropentamethylenetetramine), OBSH (4,4′-oxybisbenzenesulfonylhydrazide), hydrogen carbonate, carbonate. Etc. Examples of citrates include monosodium citrate, trisodium citrate, sodium hydrogen citrate, potassium citrate and the like. Among these, hydrogen carbonate and/or a mixture of a carbonate and a citrate are preferable, and a mixture of a hydrogen carbonate and a citrate is preferable, from the viewpoints of easy handling and high nucleation effect. Particularly preferred is a mixture of sodium hydrogen carbonate and monosodium citrate.

The ratio of the pyrolytic foaming agent and the citrate in the cell nucleating agent (the total amount of the pyrolytic foaming agent and the citrate is 100% by weight) makes it possible to obtain an efficient nucleating effect with a small addition amount. From the viewpoint of being easy, the thermal decomposition type foaming agent is preferably 10 to 90% by weight and the citrate is preferably 90 to 10% by weight, more preferably the thermal decomposition type foaming agent is 30 to 85% by weight and the citrate is 70% by weight. ˜15% by weight, more preferably 40 to 80% by weight of pyrolytic foaming agent and 60 to 20% by weight of citrate.

As the shrinkage inhibitor, conventionally known ones such as fatty acid ester, aliphatic amine and fatty acid amide can be used. The fatty acid ester is preferably an ester of a fatty acid having 8 to 30 carbon atoms and a polyhydric alcohol having 3 to 7 hydroxyl groups. Examples of the fatty acid having 8 to 30 carbon atoms include lauric acid, oleic acid, stearic acid, behenic acid, lignoceric acid, cerotic acid, heptacoic acid, montanic acid, melicinic acid and laxeric acid. Examples of the polyhydric alcohol having 3 to 7 hydroxyl groups include glycerin, diglycerin, triglycerin, erythritol arabite, xylimaat, mannitol, sorbit and sorbitan.

Examples of the aliphatic amine include dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine, docosylamine, N-methyloctadecylamine, N-ethyloctadecylamine, hexadecylpropylenediamine and octadecylpropylenediamine. ..
Examples of the fatty acid amide include stearic acid amide, oleic acid amide, erucic acid amide, methylenebisstearic acid amide, ethylenebisstearic acid amide, and lauric acid bisamide. These may use only 1 type and may use it in combination of 2 or more type.

Among these, fatty acid esters are preferable from the viewpoint that they have a small effect on foaming properties and various physical properties of the foam and have a large shrinkage-preventing effect, and among these ester compounds, partial ester compounds rather than these complete ester compounds, particularly A monoester compound is preferable because a more remarkable shrinkage preventing effect can be obtained, and stearic acid monoglyceride, behenic acid monoglyceride, or a mixture of stearic acid monoglyceride and behenic acid monoglyceride is further preferable.

In the non-crosslinked polyethylene resin extruded foam board according to the present invention, the ratio B/A of the addition amount B of the shrinkage preventing agent to the addition amount A of the cell nucleating agent is 0.3 or more and 4.0 or less. Is characterized by. By setting the ratio B/A of the addition amount B of the shrinkage-preventing agent to the addition amount A of the bubble-nucleating agent to 0.3 to 4.0, the addition amount of the bubble nucleating agent and the shrinkage-preventing agent can be individually adjusted. Regardless, it has a desired cell diameter and is capable of satisfying both a high closed cell rate and weather resistance. The range of the above ratio is preferably 0.4 to 3.0, more preferably 0.5 to 2.0.

When the amount of the cell nucleating agent added is increased, the cell diameter of the obtained foam tends to be small, but if it exceeds the appropriate amount, the closed cell ratio may be reduced. Therefore, the addition amount in the present invention is preferably 0.03 to 1.3 parts by weight, more preferably 0.08 to 1.0 parts by weight, and still more preferably 0.1 to 100 parts by weight of the polyethylene resin. 0.8 parts by weight.

From the viewpoint of imparting a proper shrinkage-preventing effect to the foam, the lower limit of the addition amount of the shrinkage-preventing agent is preferably 0.1 part by weight or more based on 100 parts by weight of the polyethylene-based resin. The upper limit is more preferably 1.5 parts by weight or less because it is difficult to coarsen the bubble diameter. It is more preferably 0.3 to 1.3 parts by weight, and even more preferably 0.4 to 1.2 parts by weight.

The non-crosslinked polyethylene resin extruded foam board according to the present invention contains a weather resistant agent. Antioxidants, ultraviolet absorbers, hindered amine light stabilizers (HALS) and the like can be used as the weather resistance agent.

Among these, it is preferable to use an ultraviolet absorber, HALS, and a mixture of an ultraviolet absorber and HALS, because a small amount has a large effect of improving the weather resistance as a foam. An antioxidant can be used together.
Examples of the ultraviolet absorber include a triazine ultraviolet absorber, a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a benzoate ultraviolet absorber, and a cyanoacrylate ultraviolet absorber. These may be used alone or in combination of two or more.

Examples of the triazine-based ultraviolet absorber include 2,4-diphenyl-6-(2-hydroxy-4-methoxyphenyl)-1,3,5-triazine and 2,4-diphenyl-6-(2-hydroxy-). 4-ethoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy-4-propoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-(2-hydroxy- 4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-butoxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-( 2-Hydroxy-4-hexyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-octyloxyphenyl)-1,3,5-triazine, 2,4 -Diphenyl-6-(2-hydroxy-4-dodecyloxyphenyl)-1,3,5-triazine, 2,4-diphenyl-6-(2-hydroxy-4-benzyloxyphenyl)-1,3,5 -Triazine and the like.

Examples of the benzophenone-based ultraviolet absorber include 2,4-dihydroxy-benzophenone, 2-hydroxy-4-methoxy-benzophenone, 2-hydroxy-4-n-octoxy-benzophenone, 2-hydroxy-4-dodecyloxy-benzophenone, and the like. 2-hydroxy-4-octadecyloxy-benzophenone, 2,2'-dihydroxy-4-methoxy-benzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-benzophenone, 2,2',4,4' -Tetrahydroxy-benzophenone and the like.

Examples of the benzotriazole-based ultraviolet absorber include 2-(2'-hydroxy-5-methylphenyl)benzotriazole and 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole. , 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy- 3',5'-di-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3' ,5'-Di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-(3",4",5",6"-tetrahydrophthalimidomethyl)-5'- Methylphenyl)benzotriazole, 2,2-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol), 2-(2'-hydroxy -3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, (2 (2'-Hydroxy-3',5'-di-tert-amylphenyl)-5-chlorobenzotriazole, 2(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chloro Examples thereof include benzotriazole and (2(2′-hydroxy-3′,5′-di-tert-amylphenyl)-5-chlorobenzotriazole.

Examples of the benzoate-based ultraviolet absorber include 2,4-di-t-butylphenyl-3′,5′-di-t-butyl-4′-hydroxybenzoate and 2,6-di-t-butylphenyl-. 3',5'-di-t-butyl-4'-hydroxybenzoate, n-hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate and n-octadecyl-3,5-di-t-butyl -4-hydroxybenzoate etc. are mentioned.

Examples of the cyanoacrylate-based ultraviolet absorber include 2'-ethylhexyl-2-cyano-3,3-diphenyl acrylate, ethyl-2-cyano-3-(3',4'-methylenedioxyphenyl)-acrylate and the like. Are listed.

Among these UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and benzoate-based UV absorbers are preferable from the viewpoint of compatibility with resins and volatility during processing.

Examples of the hindered amine light stabilizer (HALS) include dimethyl succinate 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, poly{[(6 -(1,1,3,3-Tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl)[2-(2,2,6,6-tetramethyl-4-piperidyl)imino ] Hexamethylene [4-(2,2,6,6-tetramethyl-4-piperidyl)imino]], N,N'-bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-] N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5 triazine condensate, 2,2,6,6-tetramethylpiperidin-4-ol The esterification reaction product of and the like. These may be used alone or in combination of two or more. Among them, poly{[(6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl)[2-(2,2,6,6- Tetramethyl-4-piperidyl)imino]hexamethylene[4-(2,2,6,6-tetramethyl-4-piperidyl)imino]], 2,2,6,6-tetramethylpiperidin-4-ol It is preferable to use an esterification reaction product because the effect of weathering stability is higher.

Examples of antioxidants include phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, and the like. These 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]. Methane, 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]ethylisocyanate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris(3,3 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], triethyleneglycol-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) (cheminox 1129), 2,2'-butylidene -Bis-(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, Examples include tocopherols.

As the phosphorus-based antioxidant used in the present invention, the same ones as those added to a normal polyolefin-based resin can be used, and they may be used alone or in combination of two or more kinds.

Examples of phosphorus-based antioxidants include tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite, distearyl pentaerythritol 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-ethylhexylphosphite, 2,2'-ethylidenebis(4,6-di-t-butylphenyl)fluorophosphite, bis(2,4 -Di-t-butyl-6-methylphenyl)ethyl phosphite, 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'-tra-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 Phosphopine 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-tert-butyl disulfide, di-tert-amyl disulfide. , Dicyclohexyl disulfide, di-tert-octyl disulfide, di-n-dodecyl disulfide, di-tert-dodecyl disulfide and the like.

The amount of the weatherproofing agent used in the present invention is 0.01 part by weight or more and 3 parts by weight or less, preferably 0.05 part by weight, with respect to 100 parts by weight of the raw material resin component, from the viewpoint of imparting desired weatherability. The amount is 1 part by weight or more and 1 part by weight or less, more preferably 0.08 parts by weight or more and 0.5 parts by weight or less.

Examples of the foaming agent usable for the non-crosslinked polyethylene resin extruded foam board of the present invention include aliphatic hydrocarbons such as propane, normal butane, isobutane, normal pentane, isopentane, and hexane; and fats such as cyclopentane and cyclobutane. Examples thereof include cyclic hydrocarbons; ethers such as dimethyl ether, diethyl ether and methyl ethyl ether; alcohols such as methanol and ethanol; inorganic gases such as air, nitrogen and carbon dioxide; and water. These foaming agents may be used alone or in combination of two or more. Among these, aliphatic hydrocarbons are preferable, and normal butane and/or isobutane are particularly preferable, from the viewpoint that the desired expansion ratio, closed cell ratio, and average cell diameter can be easily obtained. The amount of the foaming agent added may be appropriately adjusted because it depends on the type of the foaming agent and the foaming ratio of the target foam, but it may be appropriately adjusted. 0.5 to 20 parts by weight is preferable, and 1 to 15 parts by weight is more preferable.

In the present invention, it is possible to add a cell nucleation auxiliary agent for the purpose of promoting the effect of the cell nucleation agent. Examples of the bubble nucleation auxiliary agent include talc, silica, calcium carbonate, zeolite, zinc white, and lithium compounds. Examples of lithium compounds include lithium acetate, lithium oxalate, lithium citrate, lithium carbonate, and boric acid. Lithium etc. can be raised. Above all, a lithium compound is preferably contained, and more preferably lithium carbonate is contained, because it is highly effective in reducing the cell diameter when used in combination with the cell nucleating agent. A powdery one may be directly added to these bubble nucleation auxiliary agents, or a masterbatch considering the compatibility with the main material (raw material resin component) may be used.

As a raw material resin component, a synthetic resin may be added in addition to the polyethylene resin as long as the effect of the present invention is not impaired.

Examples of synthetic resins other than polyethylene resins include polyolefin resins other than polyethylene resins, polyester resins, polyamide resins, styrene resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, and polyamide-polyol copolymers. And the like, thermoplastic elastomers such as polyamide-based elastomers, polyvinyl chloride-based elastomers and polybutadiene-based elastomers.

Examples of the polyolefin resin other than the polyethylene resin include propylene, 1-butene, and other α-olefins having 3 to 4 carbon atoms, and copolymers containing these as the main components. Specific examples of these polyolefin resins include not only homopolymers such as polypropylene and poly-1-butene, but other 5 to 20 carbon atoms as long as the main component is an α-olefin having 3 to 4 carbon atoms. And α-olefins or copolymers with vinyl compounds such as vinyl acetate, vinyl chloride, acrylic acid, methacrylic acid and styrene. Further, a graft copolymer graft-modified with an unsaturated carboxylic acid such as maleic anhydride, maleic acid or acrylic acid or a derivative thereof may be used. Further, these polyolefin resins may be a mixture.

The addition amount of the other synthetic resin can be appropriately set as long as the effect of the present invention is not impaired, but for example, it is preferably 0 to 30 parts by weight, and 0 to 15 parts by weight based on 100 parts by weight of the polyethylene resin. More preferably, it is parts by weight.

In the present invention, if necessary, a crystal nucleating agent, a heat stabilizer, an antistatic agent, a conductivity-imparting agent, a functional additive such as a flame retardant, a lubricant, an inorganic filler, an additive such as a pigment is added. You may.

In the present invention, the addition of the colorant is not limited, and a natural color can be obtained without adding the colorant, or a desired color can be obtained by adding a colorant such as blue, red or black. .. 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.

The non-crosslinked polyethylene-based resin extruded foam board of the present invention has a foaming ratio in the range of 5 to 30 times, so that it has good workability as a cushioning material, which is one of the main applications, and it is suitable for lightweight parts to heavy parts. It can be used as a cushioning material for a wide range of conveyed products. The expansion ratio is appropriately selected depending on the weight of the product, but the lower limit is preferably 6 times, and more preferably 7 times from the viewpoint of lightness, grip of the product, cushioning property, and the like. On the other hand, the upper limit value is preferably 25 times, more preferably 20 times.

The non-crosslinked polyolefin resin extruded foam board of the present invention has a viewpoint that it can be processed into various cushioning material shapes by processing, and that it is homogeneous as a cushioning material when used as a single sheet instead of a laminated body of sheets. The thickness is 20 mm or more from the viewpoint that a product is easily obtained. It is preferably 30 mm or more, more preferably 40 mm or more. The upper limit of the thickness is not particularly limited, but it is preferably 150 mm or less, more preferably 100 mm or less, and further preferably 70 mm or less, because it is difficult to secure the thickness by extrusion foaming.

The non-crosslinked polyethylene resin extruded foam board of the present invention can achieve both a fine cell diameter and a high closed cell rate. Specifically, the average cell diameter is preferably 100 μm or more, more preferably 120 μm or more, still more preferably 150 μm or more, from the viewpoint of easily adjusting the desired closed cell rate and expansion ratio. On the other hand, the average bubble diameter is preferably 600 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less, from the viewpoint of product protection in major cushioning material applications. Here, the average bubble diameter is measured by the measuring method described in Examples below.

The non-crosslinked polyethylene resin extruded foam board of the present invention has a closed cell ratio of 70% or more from the viewpoint that the cushioning performance as a cushioning material, the repeated use performance, and the dimensional recovery during punching are good. Is preferable, 75% or more is more preferable, and 80% or more is further preferable.

The method for producing a non-crosslinked polyethylene-based resin extruded foam board of the present invention (hereinafter sometimes referred to as the “production method of the present invention”) comprises a cell composed of a raw material resin component, a pyrolytic foaming agent and a citrate. A non-crosslinking polyethylene-based resin that is extruded and foamed from a die attached to the end of an extruder of a foamable polyethylene-based resin composition obtained by melt-kneading in a extruder with a nucleating agent, a shrinkage-preventing agent, a weathering agent, and a foaming agent A method for producing an extruded foam board, wherein the ratio B/A of the addition amount B of the shrinkage inhibitor to the addition amount A of the cell nucleating agent is 0.3 or more and 4.0 or less, and the weathering agent is 0.01 parts by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the raw material resin component,
Extrusion foaming is performed so that the molding coefficient α represented by the following formula (1) is 1.5 or more. ..
Forming factor α=A _F /((Q/3600)/ρ _F ) ^(2/3)・・・Equation (1)
(In the above formula (1), A _F represents the cross-sectional area (m ² ) of the non-crosslinked polyethylene resin extruded foam board, Q represents the discharge amount (kg/hr) during extrusion foaming, and ρ _F is The density of the non-crosslinked polyethylene resin extruded foam board is shown.)
According to the production method of the present invention, the non-crosslinked polyethylene resin extruded foam board of the present invention can be easily produced.

In the production method of the present invention, raw resin components (polyethylene resin, etc.) contained in the expandable polyethylene resin composition, cell nucleating agent, shrinkage inhibitor, weathering agent, foaming agent, etc. The same applies to those described above.

The production method of the present invention is characterized in that the foamable polyethylene resin composition is extruded under the condition that the molding coefficient α represented by the above formula (1) is 1.5 or more.

The molding coefficient α is an index of whether or not a foam having a large cross-sectional area can be efficiently obtained with respect to the amount (discharge amount) of the resin discharged from the die attached to the tip of the extruder. As the molding coefficient α increases, a foam having a relatively large cross-sectional area can be obtained with a small discharge amount, but the bubble diameter tends to increase at that time. In the production method of the present invention, it is possible to obtain a foam having a small cell diameter and a high closed cell rate even when the molding coefficient α is large. In the production method of the present invention, from the viewpoint that a foam having a large cross-sectional area can be obtained more efficiently, the molding coefficient α is preferably 1.7 or more, and more preferably 2.0 or more. The discharge amount, the cross-sectional area, and the density in the present invention can be appropriately set according to the device used and the desired foam.

Examples of the method of adjusting the molding coefficient α include a method of adjusting the speed of the foam extruded from a die attached to the tip of the extruder. By decreasing the speed of the foam, it is possible to increase the cross-sectional area of the foam, that is, the molding coefficient α. A device that can perform such operations is a device that has the function of adjusting the speed of the foam by pinching the foam from the top or bottom or the left and right, and the part where the foam is sandwiched is roll-shaped or belt-shaped. And the like. Further, in the manufacturing method of the present invention, it is possible to use a molding die capable of constraining the foam body vertically and/or horizontally at the tip of the die. By using the molding die, it is possible to relatively easily expand the cross-section of a foam having a small cell diameter in which it is difficult to expand the cross-sectional area of the foam.

As the apparatus used in the production method of the present invention, a known apparatus used as an extruder for polyethylene resin can be used, but the polyethylene resin and a foaming agent are mixed and cooled to a temperature suitable for foaming. It is necessary to be able to heat a kneading/cooling device such as a single-screw extruder, a twin-screw extruder, a cooling mixer, a static mixer or a kneading/cooling device such as a static mixer, or a polymeric material such as those connected in multiple stages to an appropriate temperature, Examples of the apparatus capable of kneading while applying an appropriate shear stress are not limited to these.

For example, in the first-stage extruder, the supplied raw material resin, additives and foaming agent are melt-kneaded at a temperature suitable for kneading and adjusted to a desired discharge amount, and then the second-stage extruder connected The temperature of the discharged resin can be adjusted by a machine so that the temperature is suitable for foaming, and the resin can be extruded from a die to foam. The temperature suitable for the kneading may be a temperature at which the raw material resin is surely melted and kneading with the additive or the foaming agent is preferably carried out, and in the present invention, the melting point of the raw material resin or more and The temperature at which the effect of the cell nucleating agent used is efficiently exhibited is preferable. The temperature at which the effect of the cell nucleating agent is efficiently exhibited is a temperature at which the decomposition of the decomposable foaming agent sufficiently proceeds to obtain a desired nucleating action, and for example, sodium hydrogen carbonate as the cell nucleating agent. When a mixture of and sodium monosodium citrate is used, 180-230°C is preferred. The temperature suitable for foaming is the temperature at which the expansion ratio and closed cell ratio of the polyethylene resin, which is the main raw material, are good, and the temperature of the resin discharged from the die is generally less than the resin melting point minus 10°C. It is preferably in the range of 20°C.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The test methods and criteria used in various evaluation methods in the examples and comparative examples are as follows.

<Melt flow rate (MFR)>
MFR complies with the regulation of the A method described in JIS K 7210 (1999) and uses a melt indexer S-01 (manufactured by Toyo Seiki Seisakusho Co., Ltd.) at 190° C. under a constant load (2.16 kg) for a predetermined time from the die. The value was converted from the amount of resin extruded into 2 to the amount extruded in 10 minutes.
The fixed time is 120 seconds when the melt flow rate exceeds 0.5 g/10 minutes and 1.0 g/10 minutes or less, and when the melt flow rate exceeds 1.0 g/10 minutes and 3.5 g/10 minutes or less. Is 60 seconds, 30 seconds for more than 3.5 g/10 minutes and 10 g/10 minutes or less, 10 seconds for more than 10 g/10 minutes and 25 g/10 minutes or less, 100 g/10 for more than 25 g/10 minutes If it was less than or equal to minutes, it was 5 seconds, and if it was more than 100 g/10 minutes, it was 3 seconds.
It was decided to collect three cut pieces cut at the above-mentioned fixed time and calculate the average value thereof, and if three pieces could not be taken in one measurement, the measurement was continued until three pieces could be taken. When the melt flow rate measured in a certain number of seconds was not within the corresponding range, the measurement was performed again in the number of seconds according to the melt flow rate.

<Closed cell ratio>
Three test pieces each having a width of 20 mm, a thickness of 20 mm, and a length of 30 mm were prepared from each of the foams obtained in the examples and comparative examples, and the air pycnometer (manufactured by Tokyo Science Co., Ltd.) was used in accordance with the method described in ASTM D2856. The volume Vc (cm ³ ) of the test piece was measured using an air-comparison hydrometer model 1000). Next, the same test piece after the measurement was submerged in a graduated cylinder containing ethanol, the apparent volume Va (cm ³ ) was obtained from the liquid level rise (submersion method) of the graduated cylinder, and the independent bubble ratio ( %).
Closed cell ratio (%)=(Vc/Va)×100
The measurement was carried out on three test pieces, and the average value was taken as the closed cell rate of the foam.

<Foam density>
It was calculated from the following formula from the weight W (kg) of the test piece used in the measurement of the closed cell ratio and the volume Va (m ³ ) calculated by the water immersion method.
Foam density (kg/m ³ )=W/Va
The measurement was carried out on three test pieces, and the average value was taken as the density of the foam.

<Expansion ratio>
It was calculated from the foam density (kg/m ³ ) and the resin density (kg/m ³ ) by the following formula. The resin density was measured according to JIS K7112.
Expansion ratio (times)=resin density/foam density <average cell diameter>
The foams obtained in the examples and comparative examples were cut into a length of 20 mm in the extrusion direction at three arbitrary cross-sections orthogonal to the extrusion direction to prepare sample A. Further, a cubic sample B having 5 to 10 mm on each side was cut out from the sample A at the following measurement points. Each observation surface (thickness direction, width direction, extrusion direction) of the cubic sample B was cut with a double-edged razor [feather, high-stainless double-edged blade], taking care not to break the bubble film (cell film). The cut surface was observed with a microscope [VHX-900 manufactured by KEYENCE CORPORATION]. In the obtained image, a line segment having a length of 4000 μm was drawn, the number n of bubbles passing through the line segment was measured, and the bubble diameter was calculated by the following formula.
Bubble diameter (μm) = 4000/n
This measurement was carried out for each measurement location in the thickness direction, width direction, and extrusion direction, and the arithmetic average value of these was taken as the average cell diameter (μm).
*) Measurement location: The average cell diameter at the following 5 points was measured at each of 3 locations of arbitrary cross section that were orthogonal to the extrusion direction of the foam.
・Central part (measurement point 1)
・Middle part between the center and both ends in the width direction (measurement points 2 and 3)
・Middle part between the central part and the upper and lower ends in the thickness direction (measurement points 4, 5)
<Void evaluation>
The cubic sample B was observed in the same manner as in the measurement of the average bubble diameter, and in the cavity generated by the communication of the bubbles, the sizes in the longitudinal direction and the lateral direction of the cavity were measured, and the average value was the average bubble diameter. The presence or absence of voids was evaluated with the one having 3.246 times or more.

<Foam size>
The following measurements were carried out for sample A (3 pieces) taken for measuring the average bubble diameter.
Width: Measures the horizontal dimension perpendicular to the extrusion direction. The average value of three samples was taken as the width dimension.
Thickness: For each sample, the dimension in the vertical direction perpendicular to the extrusion direction is measured at three points, that is, the width center and 30 mm inside from both ends. The average value of three samples was used as the thickness dimension.
Cross-sectional area: The cross-sectional area was calculated by multiplying the above width and thickness.

<Weather resistance evaluation>
From the foams obtained in Examples and Comparative Examples, test pieces having a length of 50 mm, a width of 50 mm and a thickness of 10 mm were cut out from the vicinity of the center in the foam thickness direction so as not to include the surface layer portion. After the test piece was left outdoors for 100 days, the surface of the test piece was lightly rubbed with a fingernail and evaluated according to the following criteria.
Can't scrape foam...○
The foam is scraped and powder is generated... ×
(Example 1)
100 parts by weight of low-density polyethylene (“C470” made by Ube Maruzen Polyethylene, MFR 2.0 g/10 min, density 918 kg/m ³ ) was mixed with 0% of a mixture of sodium hydrogencarbonate 50% and mono-citrate citrate 50% as a bubble nucleating agent. .2 parts by weight, stearic acid monoglyceride 0.5 parts by weight as an anti-shrinking agent, and 0.3 parts by weight of a benzoate-based UV absorber "Tinuvin 120" (manufactured by BASF Japan) as a weathering agent were added to obtain a Φ40 biaxial-Φ90 mm. It was fed to a single-screw tandem extruder. After melting in a first extruder (φ40 twin screw) set to 230° C., 2.0 parts by weight of isobutane as a foaming agent was press-mixed and cooled in a second extruder (φ90 mm), followed by extrusion. It was extruded at a discharge rate of 50 kg/hour under atmospheric pressure from a rectangular die (opening 50 mm×5.5 mm) connected to the machine tip. The foam extruded from the die was shaped by a molding die while controlling the speed with a molding machine to obtain a plate-shaped foam. The obtained plate-shaped foam had no void and a high closed cell rate. Table 1 shows the results of measuring and evaluating various physical properties of the obtained foam.

(Examples 2 to 6)
A plate-like foam was obtained in the same manner as in Example 1 except that the composition was changed as shown in Table 1. Table 1 shows the evaluation results of the obtained plate-like foam.

(Example 7)
A plate-like foam was obtained in the same manner as in Example 2 except that the discharge rate was 70 kg/hour. Table 1 shows the evaluation results of the obtained plate-like foam.

(Examples 8 to 12)
A plate-like foam was obtained in the same manner as in Example 1 except that the amount of isobutane used as a foaming agent was 3.5 parts by weight and the composition was changed as shown in Table 1. Table 1 shows the evaluation results of the obtained plate-like foam.

(Example 13)
A plate-like foam was obtained in the same manner as in Example 11 except that 0.1 part by weight of lithium carbonate was added as a cell nucleus formation auxiliary. Table 1 shows the evaluation results of the obtained plate-like foam.

(Comparative Example 1)
A plate-like foam was obtained in the same manner as in Example 8 except that B/A was adjusted to 5.2. The obtained foam had large cells. ..

(Comparative example 2)
A plate-like foam was obtained in the same manner as in Example 11 except that the weathering agent was not used. The obtained foam had poor weather resistance.

(Comparative example 3)
A plate-like foam was obtained in the same manner as in Comparative Example 1 except that no weathering agent was used. The obtained foam had an average cell diameter smaller than that of Comparative Example 1, but was inferior in weather resistance.

(Comparative Example 4) A plate-like foam was obtained in the same manner as in Example 8 except that the shrinkage inhibitor was not used. The obtained foam sometimes sticked to the molding die so that the surface became rough, or it contracted over time, causing wrinkles on the surface.

(Comparative example 5)
The composition was changed as shown in Table 1, the manufacturing conditions were the same as in Example 1, and an annular die (diameter 75 mm) was attached to the tip of the extruder instead of the rectangular die, and the annular die was extruded and foamed into a tubular shape. After that, the sheet-like foam was obtained by stretching and cooling with a cooling mandrel while blowing air from inside and outside, and cutting the obtained cylindrical foam with a cutter. Table 1 shows the evaluation results of the sheet foam.

As shown in Examples 1 to 13 of Table 1, the non-crosslinked polyethylene resin extruded foam board of the present invention has a large cross-sectional area, a small cell diameter, and a high closed cell rate, and It is clear that it has excellent weather resistance. Further, in Example 7, although the discharge amount was increased as compared with Examples 1 to 6, products equivalent to the plate-like foams obtained in Examples 1 to 6 were obtained. It can be seen that the non-crosslinked polyethylene resin extruded foam board can be manufactured with high productivity.

Claims (9)

Contains a cell nucleating agent consisting of a pyrolytic foaming agent and citrate, a shrinkage inhibitor, and a weathering agent,
The weather resistant agent contains 0.01 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the raw material resin component,
The ratio B/A of the addition amount B of the shrinkage-preventing agent to the addition amount A of the cell nucleating agent is 0.3 or more and 4.0 or less,
Obtained by extrusion-foaming a polyethylene-based resin composition,
A non-crosslinked polyethylene resin extruded foam board satisfying the following (a) and (b).
(A) The expansion ratio is 5 times or more and 30 times or less.
(B) The thickness is 20 mm or more. The non-crosslinked polyethylene resin extruded foam board according to claim 1, wherein the thermal decomposition type foaming agent is sodium hydrogen carbonate. The non-crosslinked polyethylene resin extruded foam board according to claim 1, wherein the shrinkage inhibitor contains a fatty acid ester. The non-crosslinked polyethylene resin extruded foam board according to any one of claims 1 to 3, wherein the shrinkage inhibitor comprises monoglyceride stearate. The non-crosslinked polyethylene resin extruded foam board according to any one of claims 1 to 4, wherein the polyethylene resin composition further contains a cell nucleation auxiliary agent. The non-crosslinked polyethylene resin extruded foam board according to claim 5, wherein the cell nucleus formation auxiliary agent contains a lithium compound. The non-crosslinked polyethylene resin extruded foam board according to any one of claims 1 to 6, wherein the non-crosslinked polyethylene resin extruded foam board has an average cell diameter of 100 µm or more and 600 µm or less. The non-crosslinked polyethylene resin extruded foam board according to any one of claims 1 to 7, wherein the non-crosslinked polyethylene resin extruded foam board has a closed cell ratio of 70% or more. Polyethylene resin, foam nucleating agent consisting of pyrolytic foaming agent and citrate, shrinkage inhibitor, weathering agent, and expandable polyethylene resin composition obtained by melt-kneading in an extruder together with a foaming agent A method for producing a non-crosslinked polyethylene resin extruded foam board by extruding foam from a die attached to the tip of an extruder,
The ratio B/A of the addition amount B of the shrinkage inhibitor to the addition amount A of the cell nucleating agent is 0.3 or more and 4.0 or less,
The weather resistance is 0.01 part by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the raw material resin component,
The foamable polyethylene resin composition is extruded and foamed under the conditions such that the molding coefficient α represented by the following formula (1) is 1.5 or more.
A method for producing a non-crosslinked polyethylene resin extruded foam board.
Forming factor α=A _F /((Q/3600)/ρ _F ) ^(2/3)・・・Equation (1)
(In the above formula (1), A _F represents the cross-sectional area (m ² ) of the non-crosslinked polyethylene resin extruded foam board, Q represents the discharge amount (kg/hr) during extrusion foaming, and ρ _F is The density (Kg/m ³ ) of the non-crosslinked polyethylene resin extruded foam board is shown.)