Polypropylene-based resin composition

Abstract

To provide a polypropylene-based resin composition with reduced aggregates due to cellulose nanofibers.SOLUTION: The polypropylene-based resin composition contains the following components (A)-(D): (A) a polypropylene-based resin; (B) cellulose nanofibers; (C) a maleic anhydride-modified polypropylene and / or a silane-modified polypropylene; and (D) a hydrogenated castor oil and / or an ester of glycerol and 12-hydroxystearic acid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polypropylene-based resin composition with reduced aggregates of cellulose nanofibers.

Background Art

[0002] Polypropylene is used in various fields such as automobiles, home appliances, stationery, films, and food containers because of its excellent physical properties and low cost. However, polypropylene is not sufficiently satisfactory in terms of strength and may undergo irreversible deformation when a strong force is applied.

[0003] Therefore, when manufacturing a resin composition containing polypropylene, a method of improving the physical properties of the resin composition by mixing fillers such as talc and glass fibers with polypropylene together with maleic anhydride-modified polypropylene has been adopted. However, these fillers have a large energy load during production, and the resin compositions obtained using these fillers have problems such as a large environmental load, for example, they can only be landfilled when discarded.

[0004] In response to that problem, cellulose nanofibers, which are nanomaterials mainly composed of plant-derived cellulose, are used to improve the physical properties of resin compositions, so that resin compositions that can be incinerated and have a low environmental load can be produced. Therefore, the development of resin compositions using cellulose nanofibers has been promoted.

[0005] As a technology related to resin compositions using cellulose nanofibers, for example, in Patent Document 1, an additive composition is proposed in which the content of (B) an alcohol-based compound having 4 to 60 carbon atoms with respect to 100 parts by mass of (A) cellulose nanofibers is 0.01 to 100 parts by mass. However, when this additive composition is mixed with a resin composition, there is a problem that aggregates of the filler are likely to occur and poor appearance is caused.

[0006] To solve this problem, Patent Document 2 proposes a technique of dispersing cellulose fibers in a hydrophobic substance such as polypropylene using a (poly)glycerol derivative (Claim 1, Specification Paragraph

[0029] , etc.). However, even with this technique, depending on the molding method, the cellulose nanofibers may not be sufficiently dispersed in the resin composition and may form aggregates, still resulting in poor appearance.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is to provide a polypropylene-based resin composition in which aggregates due to cellulose nanofibers are reduced.

Means for Solving the Problems

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by adding castor hardened oil or the like together with maleic anhydride-modified polypropylene or the like. Based on these findings, the present inventors have further conducted research and completed the present invention.

[0010] That is, the present invention consists of a polypropylene-based resin composition containing the following components (A) to (D). Component (A): Polypropylene-based resin Component (B): Cellulose nanofibers Component (C): Maleic anhydride-modified polypropylene and / or silane-modified polypropylene Component (D): Castor hardened oil and / or ester of glycerin and 12-hydroxystearic acid

Effect of the Invention

[0011] In the polypropylene-based resin composition of the present invention, since the aggregates due to cellulose nanofibers are reduced, the appearance is improved, and it can be applied to a wide range of uses from automotive interior materials to miscellaneous goods such as stationery.

Mode for Carrying Out the Invention

[0012] [Component (A): Polypropylene-based resin] The polypropylene-based resin composition of the present invention contains a polypropylene-based resin as component (A). Component (A) is a resin composed of a homopolymer of propylene (homo-PP), a block copolymer, random copolymer, graft copolymer, etc. of propylene and an α-olefin other than propylene such as ethylene and butene-1, or a mixture thereof.

[0013] In addition, various synthetic rubbers such as ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, polybutadiene, polyisoprene, chlorinated polyethylene, chlorinated polypropylene, styrene-ethylene-butadiene-styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SB block), etc. are further blended with the above resin, and those blended with natural rubber are also included in component (A).

[0014] [Component (B): Cellulose nanofiber] The polypropylene-based resin composition of the present invention contains cellulose nanofibers as component (B). Component (B) is a fiber material obtained by finely decomposing (defibrating) natural cellulose as a raw material to the nanoscale.

[0015] The size of the cellulose nanofibers as component (B) is not particularly limited as long as the fiber width is generally in the nano size (1000 nm or less). For example, it is preferably in the range of 1 to 1000 nm, more preferably in the range of 2 to 500 nm, and even more preferably in the range of 3 to 300 nm. The fiber length of the cellulose nanofibers is not particularly limited, but for example, it is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.1 to 100 μm, and even more preferably in the range of 0.1 to 50 μm.

[0016] Examples of the apparatus for performing the fibrillation treatment include a rotary shear type homogenizer, a high-pressure homogenizer, a high-pressure homogenization apparatus, a ball mill, a sand mill, an attritor, a high-pressure opposed collision type disperser, a grinder, a conical refiner, and the like.

[0017] Examples of the natural cellulose as the raw material of component (B) include cellulose derived from plants such as wood, bamboo, kenaf, hemp, jute, wood pulp, waste paper, crystalline cellulose, agricultural crop residues, and recycled pulp, animals such as jellyfish, algae, and microorganisms.

[0018] As component (B), for example, Nanoforest-PDP (trade name; manufactured by Nakagoshi Pulp Industry Co., Ltd.) and the like are commercially manufactured and sold, and these can be used in the present invention.

[0019] The blending amount of component (B) with respect to 100 parts by mass of component (A) is selected according to the physical properties required for the polypropylene-based resin composition, but is preferably 0.1 to 80 parts by mass, more preferably 0.5 to 30 parts by mass. If it is 0.1 part by mass or less, the effect of improving the physical properties is reduced, and if it exceeds 80 parts by mass, the coloring derived from the cellulose nanofibers becomes strong. Therefore, it is preferably within the above range.

[0020] [Component (C): Maleic anhydride-modified polypropylene and / or silane-modified polypropylene] The polypropylene-based resin composition of the present invention contains maleic anhydride-modified polypropylene and / or silane-modified polypropylene as component (C). Component (C) is used from the viewpoint of improving the adhesion between a polypropylene-based resin with low hydrophobicity and cellulose nanofibers with high hydrophobicity, and enhancing the effect of improving the physical properties of the polypropylene-based resin composition by cellulose nanofibers.

[0021] The maleic anhydride-modified polypropylene as component (C) is a polypropylene-based resin graft-modified with maleic anhydride. The acid value of the maleic anhydride-modified polypropylene is preferably 20 to 100 mgKOH / g, more preferably 20 to 50 mgKOH / g. When the acid value is within such a range, the effects of the present invention can be fully exerted.

[0022] As the maleic anhydride-modified polypropylene as component (C), for example, Rikaid MG-441P (trade name; manufactured by Riken Vitamin Co., Ltd.; acid value 43 mgKOH / g) and the like are commercially manufactured and sold, and these can be used in the present invention.

[0023] The silane-modified polypropylene as component (C) is a polypropylene-based resin graft-modified with an unsaturated silane compound. The unsaturated silane compound used in the graft modification is represented by the following general formula. RSiR’ n Y 3-n (Here, R represents an ethylenically unsaturated hydrocarbon group or an oxyhydrocarbon group, R’ represents an aliphatic saturated hydrocarbon group or a phenyl group. Y is a hydrolyzable organic group, and n is 0, 1 or 2.)

[0024] Specifically, in the above general formula, R is vinyl, acrylic, isopropenyl, butenyl, cyclohexenyl, or γ-(meth)acryloyloxypropyl group, etc., R' is methyl, ethyl, decyl, or phenyl group, etc., Y is methoxy, ethoxy, formyloxy, acetoxypropionyloxy, alkyl or arylamino group, etc., and preferably a trialkoxysilane in which R is vinyl or γ-(meth)acryloyloxypropyl group is used.

[0025] Examples of the silane-modified polypropylene as component (C) include Licaido KG-005P (trade name; manufactured by Riken Vitamin Co., Ltd.), Linkron XPM800HM (trade name; manufactured by Mitsubishi Chemical Corporation), etc., which are commercially produced and sold, and these can be used in the present invention.

[0026] The blending amount of component (C) with respect to 100 parts by mass of component (A) is selected according to the physical properties required for the polypropylene resin composition, but is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass. If it is 0.5 part by mass or less, the effect of improving the physical properties will be reduced, and if it exceeds 5 parts by mass, the physical properties may conversely deteriorate. Therefore, it is preferably within the above range.

[0027] [Component (D): Castor hardened oil and / or ester of glycerin and 12-hydroxystearic acid] The polypropylene resin composition of the present invention contains, as component (D), an ester of castor hardened oil and / or glycerin and 12-hydroxystearic acid.

[0028] The castor hardened oil as component (D) is obtained by hydrogenating castor oil. The iodine value of the castor hardened oil is preferably 5 or less, more preferably 3 or less.

[0029] Examples of the castor hardened oil as component (D) include Rikemal TG-12 (trade name; manufactured by Riken Vitamin Co., Ltd.; iodine value 2), etc., which are commercially produced and sold, and these can be used in the present invention.

[0030] The ester of glycerin and 12-hydroxystearic acid as component (D) is an esterification product of glycerin and 12-hydroxystearic acid. The ester may be any of a monoester form (12-hydroxystearic acid monoglyceride), a diester form (12-hydroxystearic acid diglyceride), a triester form (12-hydroxystearic acid triglyceride), or a mixture thereof.

[0031] The ester of glycerin and 12-hydroxystearic acid as component (D) can be produced by esterifying glycerin and 12-hydroxystearic acid by a known method. For example, glycerin and 12-hydroxystearic acid are introduced into a reactor, and an esterification reaction is carried out with stirring in the absence or presence of a catalyst to produce an ester of glycerin and 12-hydroxystearic acid. The temperature of the reaction is not particularly limited, but it is preferably carried out in a temperature range of 150 to 300 °C, for example. Further, in order to prevent oxidative degradation of the ester of glycerin and 12-hydroxystearic acid, it is preferable to carry out the esterification reaction while purging the inside of the reactor with nitrogen. After the esterification reaction, if necessary, vacuum distillation or washing with water after alkali neutralization may be carried out to remove unnecessary fatty acids and glycerin.

[0032] As the ester of glycerin and 12-hydroxystearic acid as component (D), for example, Recemar HC-100 (trade name; 12-hydroxystearic acid monoglyceride; manufactured by Riken Vitamin Co., Ltd.) etc. are commercially produced and sold, and these can be used in the present invention.

[0033] The blending amount of component (D) with respect to 100 parts by mass of component (A) is selected according to the degree of dispersion of the cellulose nanofibers required for the polypropylene-based resin composition, but is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass. When the blending amount of component (D) is within such a range, the effects of the present invention can be sufficiently exhibited.

[0034] As the blending ratio (mass ratio) of component (C) and component (D), preferably, component (C): component (D) is in the range of 20:80 to 90:10, more preferably in the range of 30:70 to 80:20. When it is within the above range, it is preferable because the effect of improving the physical properties of the polypropylene-based resin composition and the effect of the present invention are compatible.

[0035] In the polypropylene-based resin composition of the present invention, various additives used in this field can be blended as long as the effects of the present invention are not inhibited. For example, heat stabilizers, antioxidants, fillers, colorants, antistatic agents, antifogging agents, neutralizing agents, weathering agents, ultraviolet absorbers, flame retardants, antiblocking agents, impact resistance improvers (excluding component (B)), etc. can be mentioned.

[0036] The polypropylene-based resin composition of the present invention can be obtained by heating and kneading components (A) to (D) using a known kneader.

[0037] As the kneader, for example, a Banbury mixer, a kneader, a single-screw extruder, a twin-screw extruder, etc. can be used. Among them, considering productivity, kneading power, etc., a twin-screw extruder is preferable.

[0038] The heating temperature during kneading may be within a range where components (A) and the blended components do not deteriorate too much. Specifically, for example, it is in the range of 120 to 230°C. The kneading time varies depending on the kneader used, heating conditions, etc. For example, when using a twin-screw extruder as the kneader, it is preferably 30 seconds to 10 minutes, more preferably 1 to 5 minutes.

[0039] The polypropylene-based resin composition of the present invention can be subjected to known molding methods, such as an extrusion molding method, an injection molding method, a press molding method, a vacuum molding method, a foam molding method, etc., and can be used as a molded body of any shape. Also, before molding, it may be kneaded with an extruder or the like.

[0040] As the use of the above-mentioned molded article, for example, it can be used for stationery, containers, plastic corrugated cardboard, clear cases, blister packs, automotive interior parts, household electrical appliances, etc.

[0041] Hereinafter, the present invention will be described with reference to examples, but this is merely for explaining the present invention and does not limit the present invention.

Examples

[0042] <Production of Polypropylene-Based Resin Composition and Its Molded Article> (1) Raw materials [Component (A): Polypropylene-Based Resin] A-1: Prime Polypro J105G (trade name; homo-PP; manufactured by Prime Polymer Co., Ltd.)

[0043] [Component (B): Cellulose Nanofiber] B-1: Nanoforest-PDP (trade name; manufactured by Nakakoshi Pulp Industry Co., Ltd.)

[0044] [Component (C): Maleic Anhydride-Modified Polypropylene and / or Silane-Modified Polypropylene] C-1: Maleic Anhydride-Modified Polypropylene (trade name: Rikaid MG-441P; acid value 43 mgKOH / g; manufactured by Riken Vitamin Co., Ltd.) C-2: Silane-Modified Polypropylene (trade name: Rikaid KG-005P; manufactured by Riken Vitamin Co., Ltd.)

[0045] [Component (D): Hydrogenated Castor Oil and / or Ester of Glycerin and 12-Hydroxystearic Acid] D-1: Hydrogenated Castor Oil (trade name: Rikemal TG-12; iodine value 2; manufactured by Riken Vitamin Co., Ltd.) D-2: Ester of Glycerin and 12-Hydroxystearic Acid (trade name: Rikemal HC-100; monoglyceride of 12-hydroxystearic acid; manufactured by Riken Vitamin Co., Ltd.)

[0046] [Component (E): Other Surfactants] E-1: Monoglyceryl Stearate (Trade name: Poem PV-100; manufactured by Riken Vitamin Co., Ltd.) E-2: Triglycerol Stearate (Trade name: Rikemal VT; manufactured by Riken Vitamin Co., Ltd.) E-3: Dipentaerythritol (Trade name: Di-Penta; manufactured by Perstorp)

[0047] (2) Blending of Polypropylene-based Resin Composition The blending of the polypropylene-based resin compositions (Examples 1 to 7 and Comparative Examples 1 to 5) prepared using the above raw materials is shown in Table 1.

[0048]

Table 1

[0049] (3) Preparation of Polypropylene-based Resin Composition 0.08 times the amount of the raw materials listed in Table 1 was melt-kneaded at 200°C for 3 minutes using a small twin-screw extruder (Model: Xplore; capacity 15 cc; manufactured by DSM) and extruded into strands, and the extruded composition was cut using a pelletizer to prepare pellet-shaped polypropylene-based resin compositions (Examples 1 to 7 and Comparative Examples 1 to 5).

[0050] (4) Preparation of Polypropylene-based Resin Composition Molded Article To evaluate the obtained polypropylene-based resin compositions (Examples 1 to 7 and Comparative Examples 1 to 5), these were press-molded using a press molding machine (Model: AYSR-5; manufactured by Shindo Metal Works Co., Ltd.) under the conditions of 190°C, pressed at 5 MPa for 120 seconds and 15 MPa for 180 seconds, and then water-cooled while applying a pressure of 5 MPa to prepare sheet-shaped polypropylene-based resin composition molded articles (Prototype 1 to 12) with a thickness of 300 μm.

[0051] <Evaluation Method> Polypropylene resin composition molded products (Prototype 1 - 12) were observed at a magnification of 20 times using a microscope (Model: VHX - 950F; manufactured by Keyence Corporation) in the range of 18 mm × 13 mm to observe the aggregation state of cellulose nanofibers, and images were taken. The obtained microscope images were read using software (imageJ), and binarization by the triangle method was performed. By this binarization process, the aggregated portions where cellulose nanofibers were aggregated in the image became white. Then, using this binarized analysis image, the number of white phases (aggregates) and their average area (mm 2 ) were determined, and the ratio of the area of the white phase to the total area (18 mm × 13 mm) of the analysis image was calculated, and this was taken as the aggregate ratio (%). When detecting the white phase, only those with an area of 0.01 mm 2 or more that could be visually confirmed were targeted, and the area of the white phase with respect to the total area of the analysis image was determined by the product of the number of detected white phases and their average area. The results are shown in Table 2.

[0052]

Table 2

[0053] As is clear from the results shown in Table 1, the polypropylene resin composition molded products (Prototype 1 - 7) obtained using the polypropylene resin compositions of the present invention (Example Products 1 - 7) had a reduced aggregate ratio of cellulose nanofibers that could be visually confirmed compared to the polypropylene resin composition molded products (Prototype 8 - 12) obtained using the polypropylene resin compositions of the comparative examples (Comparative Example Products 1 - 5).

Claims

**Claim 1** A polypropylene-based resin composition containing the following components (A) to (D). Component (A): Polypropylene-based resin Component (B): Cellulose nanofiber Component (C): Maleic anhydride-modified polypropylene and / or silane-modified polypropylene Component (D): Castor hardened oil and / or ester of glycerin and 12-hydroxystearic acid

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