Method for producing polyolefin foam and foam

Abstract

To provide a production method of a foam made from polyolefin-based resin having a high melt flow rate as main raw material, through an intermediate product with increased strength without increase in the amount of a cross-linking agent so as to prevent too much increase in the size.SOLUTION: A production method of a polyolefin-based foam includes adding a foaming agent, a cross-linking agent and a nano-cellulose to a polyolefin-based resin containing 38 wt.% or more of one having a melt flow rate of 2.5 g / 10 min or more, kneading the mixture to obtain a cross-linkable foamable composition, and heating the composition to cause foaming. In the method, a step of mixing 0.1 to 0.2 parts by weight of the nano-cellulose with 100 parts by weight of the polyolefin-based resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyolefin foam made primarily from a polyolefin resin having a high melt flow rate, and a method for producing the same. [Background technology]

[0002] It is well known that a crosslinkable foamable composition is obtained by adding a blowing agent and a crosslinking agent to a polyolefin resin and kneading the mixture, and then the composition is heated to foam the composition to produce a foam (see, for example, Patent Document 1).

[0003] However, the applicant has discovered the following problems when producing foams using polyolefin resins with high melt flow rates as the main raw material. Specifically, when producing foams using such polyolefin resins as the main raw material, a blowing agent and a crosslinking agent are added to the polyolefin resin, the mixture is kneaded, and then heated to foam. However, the intermediate obtained by this process is too soft and too large in size. One possible solution to this problem is to increase the amount of crosslinking agent. However, increasing the amount of crosslinking agent leads to other problems, such as the formation of holes in the intermediate or the intermediate cracking. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-069545 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made with the above in mind, and has as its object to increase the strength of the intermediate and prevent its size from becoming too large without increasing the amount of crosslinking agent. [Means for solving the problem]

[0006] The method for producing a polyolefin foam according to the invention of claim 1 is to produce a polyolefin foam having a melt flow rate of 2.5 g / 10 min or more. low-density polyethylene The crosslinkable foamable composition is obtained by adding a blowing agent, a crosslinking agent, and nanocellulose to a polyolefin resin containing 38% by weight or more of the above, and kneading the resulting composition to heat and foam the composition to produce a foam. The process includes a step of mixing 0.1 to 0.2 parts by weight of nanocellulose per 100 parts by weight of the polyolefin resin.

[0007] According to this manufacturing method, the action of nanocellulose can increase the strength of the intermediate and prevent its size from becoming too large, without increasing the amount of crosslinking agent.

[0008] One effective embodiment of such a production method is one in which the polyolefin resin contains 80% by weight or more of a biomass-derived material.

[0009] Another effective embodiment of such a production method is one in which the polyolefin resin contains 95% or more of low-density polyethylene having a melt flow rate of 2.5 g / 10 min or more.

[0010] The polyolefin foam according to the invention of claim 4 is a foam containing a polyolefin resin as a main raw material, a blowing agent, a crosslinking agent, and nanocellulose, wherein the polyolefin resin has a melt flow rate of 2.5 or more. low-density polyethylene The polyolefin resin contains 38% by weight or more of the above, and 0.1 to 0.2 parts by weight of nanocellulose per 100 parts by weight of polyolefin resin. [Effects of the Invention]

[0011] According to the present invention, it is possible to increase the strength of the intermediate and prevent the size from becoming too large without increasing the amount of crosslinking agent. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described. In this embodiment, a crosslinkable foamable composition is obtained by adding a blowing agent, a crosslinking agent, and nanocellulose to a polyolefin resin and kneading them, and then the composition is heated to foam, thereby obtaining a foam.

[0013] Specific examples of polyolefin resins that are the main raw material for foams include biomass-derived low-density polyethylene (LDPE), petroleum-derived low-density polyethylene (LDPE) with a low melt flow rate, and petroleum-derived low-density polyethylene (LDPE) with a high melt flow rate.

[0014] Specific examples of the foaming agent include organic chemical foams such as azo compounds such as azodicarbonamide and barium azodicarboxylate, nitroso compounds such as dinitrosopentamethylenetetramine and trinitrotrimethyltriamine, hydrazide compounds such as p,p'-oxybisbenzenesulfonylhydrazide, and sulfonylsemicarbazide compounds such as p,p'-oxybisbenzenesulfonylsemicarbazide and toluenesulfonylsemicarbazide. However, inorganic foaming agents such as sodium bicarbonate can also be used.

[0015] The crosslinking agent is an organic peroxide, which is a radical generator that has a decomposition temperature equal to or higher than the flow temperature of the polyolefin resin in the polyolefin resin. It decomposes upon heating to generate free radicals, resulting in intermolecular or intramolecular crosslinking. Specific examples include dicumyl peroxide, n-butyl 4,4-bis(t-butylperoxy)valerate, 1,1-ditertiarybutyl peroxide, 1,1-ditertiarybutylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-ditertiarybutylperoxyhexane, 2,5-dimethyl-2,5-ditertiarybutylperoxyhexyne, α,α-ditertiarybutylperoxyisopropylbenzene, tertiarybutyl peroxyketone, and tertiarybutyl peroxybenzoate. However, the optimal organic peroxide must be selected depending on the raw material resin.

[0016] The additive, nanocellulose, is an extremely fine fibrous material made by breaking down cellulose, the skeletal part of plant cells, into nanometer sizes. Nanocellulose is made from plant resources such as trees, rice straw, and sugarcane pomace. Nanocellulose is light and strong (one-fifth the weight of steel, but more than five times stronger), with a large specific surface area (250m²). 2 Nanocellulose has the following characteristics: a high density (or density of 1 / g or more), little deformation due to heat (about one-fiftieth that of glass), and is plant-derived and a sustainable resource. Nanocellulose with a high aspect ratio (length is 100 times or more than the width), with a width (or diameter) of about 4 nm to 100 nm and a length of about 5 μm or more, and produced by mechanical fiberization, is called cellulose nanofiber, cellulose nanofibril, fibrillated cellulose, microfibrillated cellulose, nanofibrillated cellulose, etc. Furthermore, needle-shaped (or whisker-shaped) crystals with a width of about 10 nm to 50 nm and a length of about 100 nm to 500 nm produced by acid hydrolysis are called cellulose nanocrystals, nanocellulose crystals, etc.

[0017] For the purpose of improving the physical properties of the crosslinkable foamable composition or reducing the cost, compounding agents (fillers) that do not have a significant adverse effect on crosslinking, such as metal oxides such as zinc oxide, titanium oxide, calcium oxide, magnesium oxide, and silicon oxide, carbonates such as magnesium carbonate and calcium carbonate, various dyes, pigments, and fluorescent substances, and other commonly used compounding agents for rubber and plastics, may be added as needed.

[0018] In addition, a foaming assistant may be added depending on the type of foaming agent. Specific examples of the foaming assistant include compounds containing urea as a main component, metal oxides such as zinc oxide and lead oxide, compounds containing salicylic acid, stearic acid, etc. as a main component, in other words, higher fatty acids or metal compounds of higher fatty acids.

[0019] The procedure for producing a foam in this embodiment is essentially the same as that for producing existing foams, except that cellulose nanofibers, a type of nanocellulose, are added to the main raw material polyolefin resin. That is, a blowing agent, a crosslinking agent, and cellulose nanofibers are added to the polyolefin resin and kneaded, and then the mixture is heated and foamed to obtain a foam. This embodiment involves a first-stage foaming step for the kneaded mixture, a first removal step for removing an intermediate product after the first stage of foaming, a second-stage foaming step for the intermediate product, and a second removal step for removing a foam product after the second stage of foaming.

[0020] When mixing cellulose nanofibers with a polyolefin resin, in order to improve the dispersibility of the cellulose nanofibers in the mixture, it is preferable to prepare a masterbatch in advance by mixing a high concentration of cellulose nanofibers with the same type of resin as the main raw material of the foam, and then add this masterbatch to the main raw material resin and mix the two.

[0021] Tables 1 and 2 show specific examples of this embodiment. It goes without saying that the present invention is not limited to the following examples. Tables 3 to 5 show comparative examples of this embodiment. In Tables 1 to 5, the numbers indicate the weight ratio of each component when the total weight of the main raw material, polyethylene, is 100 parts by weight. "SEB853" is a biomass-derived low-density polyethylene with a melt flow rate of 2.7 g / 10 min. "LD YF30" is a petroleum-derived low-density polyethylene with a melt flow rate of 1.1 g / 10 min. "LD LJ600" is a petroleum-derived low-density polyethylene with a melt flow rate of 5.5 g / 10 min. "T-NC216" is a masterbatch containing 40 wt% cellulose nanofibers. The "first discharge" is indicated by "◯" when the size of the intermediate produced after the first stage of expansion is within a predetermined range, i.e., 1.4 to 2.0 times the size of the raw material before the first stage of expansion. If the size of the intermediate produced after the first stage of expansion is outside the predetermined range, it is indicated by "△" when it is 1.2 to 1.4 times or 2.0 to 2.2 times the size of the raw material before the first stage of expansion. Furthermore, if the intermediate appears to be foamed at the end of the first stage of expansion or the size of the intermediate is significantly outside the predetermined range, i.e., 1.2 times or less or 2.2 times or more the size of the raw material before the first stage of expansion, it is indicated by "X." Note that the size of the raw material before the first stage of expansion is the same in each Example and Comparative Example. The "second discharge" is indicated by "◯" when the external and internal appearance of the foam is normal, "△" when holes or cracks are present in the external and internal appearance of the foam, and "X" when holes that significantly impair the appearance of the foam are present.

[0022] [Table 1]

[0023] [Table 2]

[0024] [Table 3]

[0025] [Table 4]

[0026] [Table 5]

[0027] Example 1: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 97 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 3 parts by weight of cellulose nanofiber (melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.25 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofiber was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the blowing agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0028] Example 2: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 44 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 56 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.25 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m. 3 This is what happened.

[0029] <Example 3> Petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm 3 3 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD LJ600, density 0.930 g / cm , melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Co., Ltd.) 3 A composition consisting of 97 parts by weight of cellulose acetate (MMA, melt flow rate 5.5 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, blowing agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.25 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC Corporation) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the blowing agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m. 3 This is what happened.

[0030] Example 4: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 97 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 3 parts by weight of cellulose nanofiber (melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.5 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC Corporation) containing 40% by weight of cellulose nanofiber was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the blowing agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0031] <Example 5> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 44 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 56 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.5 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m. 3 This is what happened.

[0032] <Example 6> Petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm 3 3 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD LJ600, density 0.930 g / cm , melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Co., Ltd.) 3A composition consisting of 97 parts by weight of cellulose acetate (MMA, melt flow rate 5.5 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, blowing agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.5 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC Corporation) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the blowing agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 25 kg / m. 3 This is what happened.

[0033] Example 7: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 84 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 16 parts by weight of cellulose ether (1.1 g / 10 min, melt flow rate, manufactured by Japan Polyethylene Corporation), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.3 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.5 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the blowing agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 58 kg / m. 3 This is what happened.

[0034] Example 8: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 38 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 62 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate, manufactured by Japan Polyethylene Corporation), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.3 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 0.5 parts by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 60 kg / m. 3 This is what happened.

[0035] <Comparative Example 1> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 97 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 3 parts by weight of polyethylene terephthalate (PEPC, melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials for this Comparative Example 1 did not contain cellulose nanofibers. The apparent density of the resulting foam was 28 kg / m 3 This is what happened.

[0036] <Comparative Example 2> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 44 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 56 parts by weight of cellulose acetate (product of Japan Polyethylene Corporation, melt flow rate 1.1 g / 10 min), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials of this Comparative Example 2 did not contain cellulose nanofibers. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0037] <Comparative Example 3> Petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm 3 3 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD LJ600, density 0.930 g / cm , melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Co., Ltd.) 3 A composition consisting of 97 parts by weight of polyethylene terephthalate (PEP, melt flow rate 5.5 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials for this Comparative Example 3 did not contain cellulose nanofibers. The apparent density of the resulting foam was 28 kg / m 3 This is what happened.

[0038] <Comparative Example 4> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 84 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 16 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.3 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials for this Comparative Example 4 did not contain cellulose nanofibers. The apparent density of the resulting foam was 58 kg / m 3 This is what happened.

[0039] <Comparative Example 5> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 38 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 62 parts by weight of cellulose acetate (product of Japan Polyethylene Corporation, melt flow rate 1.1 g / 10 min), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.3 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials of this Comparative Example 5 did not contain cellulose nanofibers. The apparent density of the resulting foam was 60 kg / m 3 This is what happened.

[0040] <Comparative Example 6> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 97 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 3 parts by weight of polyethylene terephthalate (PEPC, melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.7 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials for this Comparative Example 6 did not contain cellulose nanofibers. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0041] <Comparative Example 7> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 44 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 56 parts by weight of cellulose acetate (product of Japan Polyethylene Corporation, melt flow rate 1.1 g / 10 min), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.9 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials of this Comparative Example 7 did not contain cellulose nanofibers. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0042] <Comparative Example 8> Petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm 3 3 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD LJ600, density 0.930 g / cm , melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Co., Ltd.) 3A composition consisting of 97 parts by weight of polyethylene terephthalate (PEP, melt flow rate 5.5 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.8 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials of this Comparative Example 8 did not contain cellulose nanofibers. The apparent density of the resulting foam was 25 kg / m 3 This is what happened.

[0043] <Comparative Example 9> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 84 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 16 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.8 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials of this Comparative Example 9 did not contain cellulose nanofibers. The apparent density of the resulting foam was 65 kg / m 3 This is what happened.

[0044] Comparative Example 10: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 38 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 62 parts by weight of cellulose acetate (product of Japan Polyethylene Corporation, melt flow rate 1.1 g / 10 min), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), and 0.8 parts by weight of dicumyl peroxide (DCP, crosslinking agent) was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, thereby foaming. The raw materials for this Comparative Example 10 did not contain cellulose nanofibers. The apparent density of the resulting foam was 65 kg / m 3 This is what happened.

[0045] <Comparative Example 11> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 97 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 3 parts by weight of cellulose nanofiber (melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 1 part by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofiber was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent and cause foaming, but no foaming had occurred at the time of the first removal.

[0046] <Comparative Example 12> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 44 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 56 parts by weight of cellulose nanofiber (56 parts by weight of cellulose acetate copolymer, melt flow rate 1.1 g / 10 min, manufactured by Japan Polyethylene Corporation), 16 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.5 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 1 part by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC Corporation) containing 40% by weight of cellulose nanofiber was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent and cause foaming, but no foaming had occurred at the time of the first removal.

[0047] <Comparative Example 13> Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 84 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3 A composition consisting of 16 parts by weight of cellulose acetate (1.1 g / 10 min, melt flow rate, manufactured by Japan Polyethylene Corporation), 6 parts by weight of azodicarbonamide (ADCA, foaming agent), 0.8 parts by weight of zinc oxide (ZnO, foaming aid), 0.3 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 1 part by weight of a masterbatch (model number T-NC216, manufactured by Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 70 kg / m. 3 This is what happened.

[0048] Comparative Example 14: Biomass-derived low-density polyethylene (LDPE, product name: SEB853, density 0.923 g / cm 3 38 parts by weight of petroleum-derived low-density polyethylene (LDPE, product name: Novatec LD YF30, density 0.920 g / cm), melt flow rate 2.7 g / 10 min, manufactured by Braskem 3A composition consisting of 62 parts by weight of azodicarbonamide (ADCA, foaming agent), 6 parts by weight of zinc oxide (ZnO, foaming aid), 0.8 parts by weight of dicumyl peroxide (DCP, crosslinking agent), and 1 part by weight of a masterbatch (model number T-NC216, Seiko PMC) containing 40% by weight of cellulose nanofibers was kneaded, and the kneaded mixture was heated under pressure for 45 minutes to decompose the foaming agent and crosslinking agent, resulting in foaming. The apparent density of the resulting foam was 70 kg / m. 3 This is what happened.

[0049] As described above, in Examples 1 to 8 containing 0.25 to 0.5 parts by weight of a masterbatch containing 40% by weight of cellulose nanofibers, in other words, 0.1 to 0.2 parts by weight of cellulose nanofibers, the intermediate did not foam more than necessary or not foam enough at the time of the first removal, and even when the second removal was completed, there were no abnormalities in the appearance or interior of the produced foam.

[0050] In contrast, the products described in Comparative Examples 1 to 5 were prepared by removing the master batch containing cellulose nanofibers from the raw materials of Examples 4 to 8, respectively, and adding similar processes. However, in all cases, the intermediate foamed more than necessary at the time of the first removal, resulting in a defect in that its size became too large.

[0051] In addition, the materials described in Comparative Examples 6 to 10 are the same as those of the raw materials described in Comparative Examples 1 to 5, respectively. Crosslinking In both cases, the intermediate body was within the specified size at the time of the first removal, but defects occurred in that holes and cracks appeared on the exterior and inside of the foam at the time of the second removal.

[0052] Furthermore, in the comparative examples 11 to 14, the amount of the master batch containing 40% by weight of cellulose nanofibers among the raw materials of examples 4, 5, 7 and 8 was increased to 1 part by weight (0.4 parts by weight of cellulose nanofibers). However, in all cases, problems occurred in which the intermediate did not foam at the time of the first removal or the size of the intermediate was too small.

[0053] As described above, according to the present embodiment, when a polyolefin-based foam is produced using a material containing 38% polyolefin having a melt flow rate of 2.5 g / 10 min or more, it is possible to prevent the intermediate from becoming too large in size and to prevent problems such as the formation of holes in the intermediate or the intermediate cracking, thereby enabling the foam to be suitably produced using such raw materials.

[0054] Furthermore, many biomass-derived polyolefin resins have a high melt flow rate, and it has been difficult to produce foams using such polyolefin resins. However, according to the present embodiment, foams can be suitably produced even when the polyolefin resin contains 80% by weight or more of biomass-derived components, as in Examples 1, 4, and 7.

[0055] According to this embodiment, as in Examples 1, 3, 4, 6 and 7, a foam can be suitably produced using a polyolefin resin containing 95% or more of low-density polyethylene having a melt flow rate of 2.5 g / 10 min or more as a raw material.

[0056] The present invention is not limited to the above-described embodiment.

[0057] For example, any polyolefin resin containing 38% or more of a material with a melt flow rate of 2.5 g / 10 min or higher can be used as the main raw material for the foam of the present invention, not limited to the biomass-derived low-density polyethylene and petroleum-derived low-density polyethylene described in the above-mentioned examples. In other words, the blending ratio of the polyolefin resin used as the raw material is arbitrary as long as it contains 38% or more of a material with a melt flow rate of 2.5 g / 10 min or higher. However, polyolefin resins containing 80% or more by weight of a material derived from biomass, which is a renewable raw material, are excellent from the perspective of the SDGs, and polyolefin resins containing 95% or more of low-density polyethylene with a melt flow rate of 2.5 g / 10 min or higher, which have traditionally been difficult to use as raw materials for foams, can be suitably used as raw materials for foams.

[0058] Furthermore, the main effects of the present invention can be obtained not only with cellulose nanofibers but also with other nanocelluloses added as additives.

[0059] In addition, various modifications are possible within the scope of the present invention.

Claims

1. A method for producing a polyolefin foam, which comprises the step of mixing 0.1 to 0.2 parts by weight of nanocellulose per 100 parts by weight of the polyolefin resin, by adding a blowing agent, a crosslinking agent, and nanocellulose to the polyolefin resin containing 38% by weight or more of low-density polyethylene with a melt flow rate of 2.5 g / 10 min or more, and kneading the resulting crosslinkable foamable composition.

2. 2. The method for producing a polyolefin foam according to claim 1, wherein the polyolefin resin contains 80% by weight or more of a material derived from biomass.

3. 3. The method for producing a polyolefin foam according to claim 1, wherein the polyolefin resin contains 95% or more of low-density polyethylene having a melt flow rate of 2.5 g / 10 min or more.

4. A foam containing a polyolefin resin as the main raw material, a blowing agent, a crosslinking agent, and nanocellulose, wherein the polyolefin resin contains 38% by weight or more of low-density polyethylene having a melt flow rate of 2.5 g / 10 min or more, and the foam contains 0.1 to 0.2 parts by weight of nanocellulose per 100 parts by weight of the polyolefin resin.

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