Resin composition, foam, and decorative foam

Abstract

To provide a novel resin composition that enables improvement of impact resistance.SOLUTION: The resin composition comprises a thermoplastic polyolefin and a fibrous material having an average aspect ratio of 30 to 1000, the fibrous material mainly containing cellulose, and the content of the fibrous material being within a range of 0.1 to 15 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition, a foam, and a decorated foam. [Background technology]

[0002] Thermoplastic resin foams are generally lightweight and have excellent thermal insulation, insulation, sound absorption, and shock absorption properties, and are therefore used in a variety of products, including building materials, packaging materials, and acoustics. Although foams are inferior to unfoamed materials in mechanical properties such as elastic modulus and strength, and thermal properties such as heat distortion temperature, the introduction of air bubbles makes it possible to reduce the amount of resin used compared to unfoamed materials, and so demand for foamed materials is expected to expand further in the future from the perspective of resource conservation. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-099758 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, it has been reported that the mechanical properties of plastic foams can be improved by reducing the cell size. However, since the viscosity of polypropylene and low-density polyethylene drops significantly above their melting points, it is difficult to control the cell size during foam molding.

[0005] Industrially, one method is to increase melt tension and control bubbles by adding a cross-linking agent or irradiating the molecules with electron beams to give them a branched structure, but this has the drawback of making the polymer infusible and reducing recyclability.

[0006] Furthermore, since polyolefins such as polypropylene have a molecular structure that makes crosslinking reactions difficult to proceed with, there is a demand for methods that enable the refinement of the cells in polyolefin foams and the improvement of their physical properties without the need for crosslinking treatment.

[0007] The present invention has been devised to solve the above problems, and an object of the present invention is to provide a novel resin composition capable of increasing the impact resistance of a foam, and a foam thereof. [Means for solving the problem]

[0008] [1] A resin composition comprising a thermoplastic polyolefin and a fibrous material having an average aspect ratio of 30 to 1000, The fibrous material is composed mainly of cellulose, A resin composition having a content of the fibrous material in the range of 0.1 to 15% by mass.

[0009] [2] The resin composition according to [1], wherein the content of the fibrous material is in the range of 0.1 to 4 mass %.

[0010] [3] The resin composition according to [1] or [2], further comprising a carboxylic acid anhydride-modified polyolefin.

[0011] [4] The resin composition according to [3], wherein the amount of the carboxylic acid anhydride-modified polyolefin is 0.1 to 10% by mass.

[0012] [5] The resin composition according to [1] or [2], wherein the ratio of the fibrous material to the carboxylic anhydride-modified polyolefin is within a range of 1:3 to 3:1.

[0013] [6] The resin composition according to any one of [1] to [5], wherein the thermoplastic polyolefin comprises a long-chain branched polyolefin having a branched structure having 20 or more carbon atoms.

[0014] [7] The resin composition according to [4], wherein the mass proportion of the long-chain branched polyolefin in the thermoplastic polyolefin is 5 mass % or more.

[0015] [8] The resin composition according to [1] or [2], wherein the average fiber length of the fibrous material is 100 to 2000 μm.

[0016] [9] A foam of the resin composition according to any one of [1] to [8].

[0017]

[10] A decorated foam comprising the foam according to [9] and a decorative layer laminated on the foam. [Effects of the Invention]

[0018] According to the present invention, a novel resin composition and foam that can improve impact resistance are provided. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view illustrating a foam and a decorated foam according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] (Resin composition) The resin composition contains a thermoplastic polyolefin and a fibrous filler having an average aspect ratio of 30 to 1,000.

[0021] (thermoplastic polyolefin) Thermoplastic polyolefins are polyolefins that are not crosslinked.

[0022] Examples of polyolefins include linear polyolefins such as polyethylene, polypropylene, polybutene, copolymers of ethylene and one or more α-olefins, copolymers of two or more α-olefins, and the like, and may be a mixture of any two or more of these.

[0023] Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene.

[0024] The thermoplastic polyolefin may be a so-called linear polyolefin that does not have a branched chain having 20 or more carbon atoms, or may be a long-chain branched polyolefin that has a branched chain having 20 or more carbon atoms, or may be a mixture containing these in any ratio.

[0025] The thermoplastic polyolefin preferably includes a long-chain branched polyolefin having a branched chain with 20 or more carbon atoms. The upper limit of the number of carbon atoms in the branched chain may be 100,000 or less, 1,000 or less, or 100 or less. Examples of long-chain branched polyolefins include low-density polyethylene (LDPE), long-chain branched polypropylene, and polylactic acid. Examples of polyolefins having branched chains with 20 or more carbon atoms include low-density polyethylene produced by radical polymerization, polyolefins graft-polymerized using electron beams, and high-melt-tension polypropylenes polymerized using metallocene catalysts. From the viewpoints of compatibility with polypropylene resins and recyclability, high-melt-tension polypropylenes polymerized using metallocene catalysts are more preferred. When the long-chain branched polyolefin is contained, the branched long chains become entangled, which increases the melt tension and makes it possible to suppress the bursting and coalescence of cells during foaming.

[0026] The proportion of long-chain branched polyolefin in the total of linear polyolefin and long-chain branched polyolefin may be 5% by mass or more, 10% by mass or more, 20% by mass or more, 50% by mass or more, 80% by mass or more, or even 100% by mass. Note that the thermoplastic polyolefin may contain linear polyolefin but not long-chain branched polyolefin.

[0027] In this specification, the thermoplastic polyolefin does not include the carboxylic acid anhydride-modified polyolefin described below.

[0028] In the resin composition, the amount of thermoplastic polyolefin may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0029] (Carboxylic acid anhydride modified polyolefin) It is preferable that the resin composition further contains a carboxylic acid anhydride-modified polyolefin. An example of a carboxylic acid anhydride is maleic anhydride. An example of a carboxylic acid anhydride-modified polyolefin is maleic anhydride-modified polypropylene.

[0030] The inclusion of a carboxylic anhydride-modified polyolefin in the resin composition improves the compatibility between the polyolefin and a fibrous material primarily composed of cellulose, facilitating dispersion of the fibrous material and miniaturizing cells. In particular, adding a carboxylic anhydride-modified polyolefin to the resin composition in a ratio of fibrous material to carboxylic anhydride-modified polyolefin of 1 / 3 to 3 / 1 can improve the compatibility between the fibrous material and the thermoplastic polyolefin while maintaining the strength of the foam.

[0031] In the resin composition, the amount of carboxylic acid anhydride-modified polyolefin may be 0.1% by mass or more, 0.15% by mass or more, 0.2% by mass or more, 0.25% by mass or more, 0.5% by mass or more, 10% by mass or less, 7.5% by mass or less, or 5% by mass or less. When the amount is 0.1% by mass or more, the compatibility between the polyolefin and the fibrous material is improved and they are sufficiently dispersed. When the amount is 10% by mass or less, deterioration of physical properties is suppressed.

[0032] (fibrous material whose main component is cellulose) The resin composition contains a fibrous material whose main component is cellulose.

[0033] Examples of fibrous materials whose main component is cellulose include plant fibers, recycled fibers, acetate-based fibers (diacetate and triacetate), pulp fibers, and cellulose fibers.

[0034] Examples of plant fibers include cotton and hemp.

[0035] Examples of acetate-based fibers include acetate fibers, diacetate fibers, and triacetate fibers.

[0036] Examples of regenerated fibers include rayon and cupra.

[0037] Pulp fibers are fibers obtained by removing lignin and hemicellulose from plant fibers.

[0038] The cellulose fiber is a fiber obtained by defibrating pulp fibers. The diameter of the cellulose fiber may be 1 μm or more, or may be less than 1 μm. The diameter of the cellulose fiber may be 3 nm to 10 μm. To ensure transparency, the diameter is preferably 200 nm or less, which is less than the wavelength of visible light. To ensure strength, the diameter is preferably 1 μm or less.

[0039] The cellulose in the fibrous material may be modified with a hydrophobic functional group such as fluorene.

[0040] Fibers containing cellulose as a main component, such as cellulose fibers, may contain at least one of hemicellulose and lignin in addition to cellulose. Cellulose may account for 50% by mass or more, or 70% by mass or more, of the fibrous material.

[0041] The average aspect ratio of the fibrous material containing cellulose as a main component is 30 to 1000. The average aspect ratio may be 50 or more, 100 or more, 150 or more, 200 or more, 400 or more, or 500 or more. The average aspect ratio may be 950 or less.

[0042] The average aspect ratio of a fibrous material whose main component is cellulose is defined as (average fiber length / average fiber diameter). Specifically, in a transmission electron microscope image of a resin composition such as a foam, the fiber diameter and fiber length of any 20 fibers are obtained, and the average aspect ratio can be calculated by dividing the average fiber length by the average fiber diameter. The average fiber length of the fibrous material may be 0.1 μm or more, 1 μm or more, 100 μm or more, 300 μm or more, 500 μm or more, 700 μm or more, 1000 μm or more, 3000 μm or less, or 2000 μm or less. From the viewpoint of strength, the average fiber length is preferably 100 μm or more, and more preferably 500 μm or more.

[0043] The average fiber diameter of the fibrous material may be 0.003 to 10 μm. The average fiber diameter of the fibrous material may be 0.2 μm or more, 0.3 μm or more, 0.5 μm or more, 5 μm or less, or 3 μm or less.

[0044] The amount of the fibrous material containing cellulose as a main component in the resin composition is 0.1 to 15% by mass, and may be 0.2% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 1.0% by mass or more, 13% by mass or less, or 10% by mass or less.

[0045] By setting the amount of cellulose-based fibrous material to 0.1% by mass or more, the effect of improving mechanical properties is easily realized. In particular, by setting the amount to 15% by mass or less, the tendency for the cells to become too fine, resulting in thin cell walls and breakage, and as a result, the tendency for the cell diameter to become large can be suppressed. Furthermore, by setting the amount of cellulose-based fibrous material to 0.1% by mass or more and 4% by mass or less, the viscosity of the resin before foaming becomes appropriate, allowing for the production of high-strength foams regardless of the molding method.

[0046] (coloring agent) The resin composition may contain a colorant. Examples of the colorant include dyes and pigments. Examples of the pigment include inorganic pigments such as metal oxides, such as titanium oxide and iron oxide, and composite oxides, such as iron-zinc oxide, chromium-antimony oxide, and iron-aluminum oxide.

[0047] The hue of the resin composition can be appropriately selected depending on the type of colorant.

[0048] The amount of the colorant in the resin composition may be 0.1% by mass or more and 30% by mass or less.

[0049] (Other ingredients) The resin composition may contain other components, such as elastomers, ultraviolet absorbers, light stabilizers, inorganic materials such as calcium carbonate, mica, and talc, flame retardants such as metal hydrates, pigments, foaming regulators, lignin, hemicellulose, antioxidants, nucleating agents, antistatic agents, processing stabilizers, slip agents, and foaming agents.

[0050] (Embodiments of Resin Composition) The resin composition may be a dry blend of the above components, a melt blend of the above components after melt-kneading (for example, a so-called compound such as pellets), or a foam. The dry blend of the resin composition can be obtained by mixing the above raw materials using a known powder blender. In the dry blend, at least one of the components constituting the resin composition may be compounded (e.g., pellets) with other components in advance by melt-kneading or the like. The melt blend of the resin composition can be obtained by melt-kneading the above dry blend in a single-screw kneader or the like, and then pelletizing the mixture as needed. (foam) As shown in Fig. 1, a foam 100 of the resin composition has a solid portion 10 of the resin composition and cells 20. In the solid portion 10, the resin composition is a melt blend.

[0051] The average diameter of the cells 20 may be 0.01 mm to 10.0 mm or less, provided that the average diameter is equal to or less than the thickness of the foam.

[0052] The diameter of each bubble (cell) is the average of the long and short diameters of the cell, and the average diameter of the bubble (cell) is defined as the arithmetic mean value of the diameters of 10 cells randomly extracted from a cross-sectional image obtained by a scanning electron microscope or the like.

[0053] As shown in Figure 1, the foam has numerous cells 20. The foam 100 may have either an open-cell structure or a closed-cell structure, but is preferably a closed-cell structure from the standpoint of mechanical properties.

[0054] (Foam shape) The shape of the foam is not particularly limited, and may be a plate, block, sheet, sphere, cone, polygonal pyramid, cylinder, polygonal pillar, or irregular shape. It may also be a shape obtained by cutting out a portion of any of these, or a combination thereof. The surface layer may also be embossed with irregularities. A foam can be molded into a desired shape by foaming a resin composition containing a foaming agent in an appropriate mold.

[0055] When the foam is in the form of a plate, the thickness thereof may be 0.5 mm or more, or 1.0 mm or more, and may be 15.0 mm or less, or 10.0 mm or less.

[0056] The expansion ratio of the foam may be 0.1 to 10 times.

[0057] (Method for producing foam of resin composition) Next, as an example of a method for producing a foam of the above-mentioned resin composition, a case where a chemical foaming agent is used will be described, although it goes without saying that a physical foaming agent may also be used.

[0058] First, a thermoplastic polyolefin, an optional carboxylic acid anhydride-modified polyolefin, a fibrous material, and a chemical foaming agent are prepared. The polyolefin is preferably in the form of pellets. The fibrous material is also preferably in the form of polyolefin masterbatch pellets. The raw materials do not contain a crosslinking agent.

[0059] There are no particular limitations on the chemical foaming agent, and various inorganic and organic foaming agents can be used.

[0060] An example of an inorganic foaming agent is baking soda (sodium bicarbonate).

[0061] Examples of chemical foaming agents include azo compounds such as azodicarbonamide (ADC) and azobisisobutyronitrile (AIBN), hydrazine derivatives, etc. These chemical foaming agents can be decomposed by heating to generate gas.

[0062] Next, the components of the resin composition, such as pellets, and the chemical foaming agent are melted and kneaded using a uniaxial molding machine or the like to obtain a molten resin, which is then injected into a mold and foamed. Alternatively, the molten resin may be pelletized once to obtain pellets of the resin composition, and then the pellets may be re-melted and fed into a mold.

[0063] Specifically, for example, a core-back molding method is suitable, in which molten resin is supplied to a cavity of a mold, and then the cavity volume is expanded to promote foaming.

[0064] (Mechanism of action) The resin composition according to the present embodiment can improve the impact resistance of a foam. Although the reason for this is not clear, it is thought that the fibrous material, which is mainly composed of cellulose and has a relatively large average aspect ratio, acts as a foam nucleating agent, resulting in finer and more uniform cell diameters and improved impact resistance.

[0065] (decorative foam) An example of a decorative foam 300 of the present invention will be described with reference to FIG.

[0066] As shown in FIG. 1, the decorated foam 300 includes at least a foam 100 and a decorative layer 200 provided on the surface of the foam 100 .

[0067] The decorative layer 200 may be a separately formed decorative sheet, and in this case, the decorative sheet may be laminated on the foam 100 via an adhesive.

[0068] The decorative layer 200 may be a dried / cured product of paint applied to the surface of the foam 100. The paint can be applied using a known printing method.

[0069] The decorative layer can have any pattern. Addition of the decorative layer can further improve mechanical properties such as impact resistance.

[0070] The decorative layer may contain a resin and a colorant such as a pigment, etc. The amount of the colorant in the decorative layer may be 0.1% by mass or more and 30% by mass or less. [Example]

[0071] (Examples 1 to 10, 13 to 26, Comparative Examples 1 to 4) The materials of each example and comparative example listed in Tables 1 to 3 were dry blended and supplied in fixed amounts to the resin charging hopper of a core-back driven injection molding machine. The dry blend was melted and kneaded in a single-screw kneader in the molding machine to obtain a molten resin composition, which was then supplied to a mold and foamed.

[0072] The thermoplastic polyolefins (other than carboxylic anhydride-modified polyolefins) used were linear polypropylene (Y-2000GP, manufactured by Prime Polymer Co., Ltd.) and long-chain branched polypropylene (MFX3, manufactured by Japan Polypropylene Corporation), the carboxylic anhydride-modified polyolefin used was maleic acid-modified polypropylene (UMEX 1001, manufactured by Sanyo Chemical Industries, Ltd.), the fibrous material used was cellulose fiber (manufactured by Sugino Machine: diameter 1 μm or more), and the chemical foaming agent used was sodium bicarbonate. The long-chain branched polypropylene had a branched chain with 20 or more carbon atoms.

[0073] The aspect ratio of the cellulose-based fibers in the resin composition was adjusted by, for example, adjusting the screw rotation speed in the single-screw kneader, the kneading time, the number of kneading cycles, etc. Adjusting each condition changes the fiber length and / or fiber diameter, which in turn changes the aspect ratio.

[0074] In Tables 1 to 3, the amounts of linear polypropylene, long-chain branched polypropylene, maleic acid-modified polypropylene, and cellulose fiber (CF) are the mass percentages relative to all components other than the chemical blowing agent, i.e., the total of all polypropylenes other than maleic acid-modified polypropylene, maleic acid-modified polypropylene, and cellulose fiber. The amount of the chemical blowing agent is expressed in parts by mass relative to 100 parts by mass of all components other than the chemical blowing agent.

[0075] Core-back method: A 100mm x 100mm x 2mm (thickness) mold was prepared as the molding die. The mold was driven in the thickness direction by 2mm (equivalent to a 4mm molded product thickness and double foaming) in conjunction with the core-back drive of the injection molding machine, expanding the cavity volume and molding. The filling speed was 30mm per second, the injection time was 2.2 seconds, the holding pressure was 15MPa, the time until the mold opened was 10 seconds, and the time until the mold was released was 0.5 seconds. A 4mm thick foam was obtained.

[0076] Short shot method: A 100mm x 100mm x 4mm (thickness) mold was prepared. Resin was filled to 50% of the mold volume, and the bubbles were allowed to expand until the mold was completely filled. A foam with a thickness of 4mm was obtained.

[0077] Furthermore, in Example 11, the surface of the foamed molded body was subjected to corona treatment, and then PP primer spray (manufactured by Rock Paint, product number: 062-4005) was sprayed on it, and then acrylic lacquer spray ECO (manufactured by Rock Paint) was used to paint it, thereby producing the foamed body of Example 9.

[0078] Furthermore, in Example 12, the surface of the foamed molded body was subjected to corona treatment, and then a polypropylene-based decorative sheet (101 Eco Sheet, manufactured by TOPPAN Corporation) was attached using an adhesive (Bond GP100) to produce the foamed body of Example 10.

[0079] (evaluation) (shock resistance) A φ12.7mm striking die is attached to a DuPont testing machine (manufactured by Tester Sangyo). The sample is placed under the striking die and a 500g weight (iron ball) is dropped from a height of 500mm. The test is carried out with N=5, with the measurement position of the sample being shifted. A depth gauge (manufactured by Mitutoyo) is used to measure the amount of dent in the sample, and the average value is used to evaluate. The amount of dent refers to the depth from the top surface of the most dented part. The measurement method was to place the depth gauge on the dented part and measure.

[0080] (Measurement of foam cell diameter) The foam is cut with a cutter, the cut surface is observed under a microscope (Keyence), and the diameters of 10 cells are measured using a two-point distance measuring tool, and the average value is used for evaluation. However, if the cell shape is not a perfect circle, the diameter of the major axis is used.

[0081] The conditions and results are shown in Tables 1 to 4.

[0082] [Table 1] [Table 2] [Table 3] [Table 4]

[0083] In Examples 1 to 26, the impact resistance could be increased. [Explanation of symbols]

[0084] 100...foam, 200...decorative layer, 300...decorative foam.

Claims

1. A resin composition comprising a thermoplastic polyolefin and a fibrous material having an average aspect ratio of 30 to 1000, The fibrous material is composed mainly of cellulose, A resin composition having a content of the fibrous material in the range of 0.1 to 15 mass%.

2. The resin composition according to claim 1, wherein the content of the fibrous material is in the range of 0.1 to 4 mass %.

3. The resin composition according to claim 1 or 2, further comprising a carboxylic acid anhydride-modified polyolefin.

4. The resin composition according to claim 3, wherein the amount of the carboxylic acid anhydride-modified polyolefin is 0.1 to 10% by mass.

5. The resin composition according to claim 3, wherein the ratio of said fibrous material to said carboxylic acid anhydride-modified polyolefin is in the range of 1:3 to 3:

1.

6. The resin composition according to claim 1 or 2, wherein the thermoplastic polyolefin comprises a long-chain branched polyolefin having a branched chain having 20 or more carbon atoms.

7. The resin composition according to claim 6 , wherein the mass ratio of the long-chain branched polyolefin to the thermoplastic polyolefin is 5 mass % or more.

8. The resin composition according to claim 1 or 2, wherein the average fiber length of the fibrous material is 100 to 2000 μm.

9. A foam of the resin composition according to claim 1 or 2.

10. A decorated foam comprising the foam according to claim 9 and a decorative layer laminated on the foam.

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