JP2014169424A - Molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding excellent in stress crack resistance.SOLUTION: The molding contains: an ethylenic copolymer which contains a polymerization unit derived from ethylene and a polymerization unit derived from at least one copolymerization compound selected from the group consisting of a vinyl ester, an unsaturated carboxylic acid, a derivative of a vinyl ester, and a derivative of an unsaturated carboxylic acid, wherein the content ratio of the polymerization unit derived from the copolymerization compound is 5-50 mass%; and cellulosic fibers having an average fiber diameter of 500 nm or less. The cellulosic fibers are contained in an amount of 0.5-10 pts.mass based on 100 pts.mass of the ethylenic copolymer.

Description

  The present invention relates to a molded body.

  Molded articles containing an ethylene copolymer are widely used in various containers and packaging materials due to their moderate flexibility and excellent mechanical properties and moldability. In particular, in applications such as pipes, bottles, bottle caps, and artificial turf, they are exposed to stresses such as internal pressure for a long time in a state where various liquids are in contact. Therefore, it is required that cracks and destruction do not occur (hereinafter also referred to as “stress crack resistance”) when left in chemicals under a certain stress.

  It has been found that increasing the molecular weight of the ethylene-based copolymer is effective in increasing the stress crack resistance, but if the molecular weight is simply increased, the fluidity and rigidity are lowered. In addition, the stress crack resistance can be increased by reducing the density, but the decrease in density is accompanied by a decrease in rigidity, and therefore cannot be applied depending on the application.

  As another method, in order to improve the mechanical properties of the resin, it has been studied to combine the resin with glass fiber, carbon fiber, or aramid fiber, thereby improving strength, rigidity, etc. Has been found to do. For example, Patent Documents 1 and 2 describe composite materials using glass fibers.

Japanese Patent No. 3166814 Japanese Patent No. 4217284

  However, the composite material of resin and glass fiber described in Patent Documents 1 and 2 has an insufficient reinforcing effect due to breakage of the glass fiber. Moreover, since the interface strength between the glass fiber and the resin is weak, there is a problem that the stress crack resistance is insufficient.

  This invention is made | formed in view of the said problem, and it aims at providing the molded object which is excellent in stress crack resistance.

  The present inventors diligently studied to solve the above problems. As a result, it has been found that the above-mentioned problems can be solved by dispersing predetermined cellulose fibers in the ethylene copolymer without agglomeration, and the present invention has been completed.

That is, the present invention is as follows.
[1]
Containing a polymerized unit derived from ethylene and a polymerized unit derived from at least one copolymer compound selected from the group consisting of vinyl esters, unsaturated carboxylic acids, derivatives of vinyl esters, and derivatives of unsaturated carboxylic acids, An ethylene copolymer in which the content of the polymerized units derived from the copolymer compound is 5 to 50% by mass;
Cellulosic fibers having an average fiber diameter of 500 nm or less,
The cellulose fiber is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the ethylene copolymer.
Molded body.
[2]
The molded product according to [1] above, wherein the ethylene copolymer includes an ethylene-vinyl acetate copolymer.

  ADVANTAGE OF THE INVENTION According to this invention, the molded object which is excellent in stress crack resistance can be provided.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. However, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof. Is possible.

[Molded body]
The molded body of this embodiment is
Containing a polymerized unit derived from ethylene and a polymerized unit derived from at least one copolymer compound selected from the group consisting of vinyl esters, unsaturated carboxylic acids, vinyl ester derivatives, and unsaturated carboxylic acid derivatives, An ethylene copolymer in which the content of the polymerization unit derived from the copolymer compound is 5 to 50% by mass with respect to the ethylene copolymer;
Cellulosic fibers having an average fiber diameter of 500 nm or less,
The cellulose fiber is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the ethylene copolymer.

[Ethylene copolymer]
The ethylene copolymer of this embodiment is a copolymer of ethylene and at least one copolymer compound selected from the group consisting of vinyl esters, unsaturated carboxylic acids, vinyl ester derivatives and unsaturated carboxylic acid derivatives. It is a polymerized copolymer. In the present specification, the “copolymerization compound” refers to vinyl ester, unsaturated carboxylic acid, vinyl ester derivative and unsaturated carboxylic acid derivative copolymerized with ethylene.

  Although it does not specifically limit as said vinyl ester, Specifically, vinyl acetate, vinyl propionate, vinyl butyrate, etc. are mentioned.

  The unsaturated carboxylic acid is not particularly limited, and specific examples include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid and the like.

  Furthermore, the derivative of the unsaturated carboxylic acid is not particularly limited, and specific examples include methyl acrylate, ethyl acrylate, ethyl methacrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate.

  Although it does not specifically limit as an ethylene-type copolymer, For example, ethylene-vinyl acetate copolymer (henceforth "EVA"), ethylene-acrylic acid copolymer (henceforth "EAA"). , Ethylene-methacrylic acid copolymer (hereinafter also referred to as “EMAA”), ethylene-methyl acrylate copolymer (hereinafter also referred to as “EMA”), ethylene-ethyl acrylate copolymer (hereinafter referred to as “ EEA ”) and ethylene-ethyl methacrylate copolymer (hereinafter also referred to as“ EMMA ”). Among these, it is preferable that an ethylene-type copolymer contains EVA. Thereby, the dispersibility of the cellulose fiber in a molded object becomes higher, and a molded object becomes more excellent in stress crack resistance.

  The content ratio in which the polymerization unit derived from the copolymer compound is contained in the ethylene copolymer is 5 to 50% by mass, preferably 10 to 35% by mass, and 12 to 30% by mass with respect to the ethylene copolymer. More preferred. When the content is 5% by mass or more, the dispersibility of the cellulosic fibers in the molded article becomes good without adding a dispersant, and the stress crack resistance is more excellent. Further, when the content is 50% by mass or less, the resin is not excessively flexible and is preferable as a material.

  Further, the melt mass flow rate (MFR, JIS-K-7210: 1999, 190 ° C., load 2.16 kg) of the ethylene-based copolymer used in the present embodiment is 0.1 to 100 g / 10 min. Preferably, it is 0.5 to 50 g / 10 min, more preferably 1.0 to 30 g / 10 min. When the MFR is 0.1 g / 10 min or more, the dispersibility of the cellulosic fibers in the molded product tends to be more excellent, the flowability of the ethylene copolymer is better, and the molding process is easier. Tend to be. Moreover, since MFR is 100 g / 10min or less, since it has moderate molecular weight, it exists in the tendency for the mechanical characteristic of a molded object to be more excellent.

  The polymerization method of the ethylene copolymer is not particularly limited, and can be performed by a known method such as a high-pressure method or a medium-low pressure method. The primary structure of the ethylene copolymer may be any structure such as random or block.

[Cellulose fiber]
Cellulosic fibers having an average fiber diameter of 500 nm or less are dispersed in the molded body of this embodiment. Although it does not specifically limit as a cellulose fiber of this embodiment, For example, the homopolymer of a cellulose, its derivative (s), or those mixtures are mentioned. Such cellulosic fibers are not particularly limited, and specific examples include wood pulp, non-wood pulp, bacteria, algae, and sea squirt-derived cellulose. Cellulosic fibers are usually subjected to chemical methods by acid hydrolysis using acids such as sulfuric acid and hydrochloric acid, or mechanical energy such as high-pressure homogenizers, refiners, grinders, ball mills, rod mills, stone mills, etc. Although it can be obtained by a physical method for miniaturization, it is not limited thereto. Commercially available cellulosic fibers that have been treated by chemical and physical methods can also be used. By the above treatment, the average fiber diameter of the cellulosic fibers can be adjusted to 500 nm or less, preferably 100 nm or less.

(Average fiber diameter)
The average fiber diameter of the cellulosic fibers is 500 nm or less, preferably 300 nm or less, and more preferably 100 nm or less. The average fiber diameter is preferably 10 nm or more, more preferably 15 nm or more, and further preferably 20 nm or more. When the average fiber diameter is 500 nm or less, the stress crack resistance of the obtained molded body is further improved. Further, when the average fiber diameter is 10 nm or more, energy used for pulverization becomes smaller and reaggregation tends not to occur. In addition, an average fiber diameter can be calculated | required by the method as described in an Example.

  The molded body of this embodiment is obtained by dispersing cellulose fibers in an ethylene copolymer. In the molded body of the present embodiment, the content of the cellulose fiber is 0.5 to 10 parts by mass, preferably 1 to 10 parts by mass, with respect to 100 parts by mass of the ethylene copolymer. More preferably, it is part by mass. When the content is 0.5 part by mass or more, the stress crack resistance is more excellent. Moreover, when content is 10 mass parts or less, the fluidity | liquidity at the time of a process becomes a more suitable range, and it is excellent by a moldability.

(Distribution method)
The molded body of the present embodiment is obtained by dispersing cellulose fibers in an ethylene copolymer without agglomeration. Although the dispersion method is not particularly limited, for example, a method of adding cellulosic fibers while melt-kneading an ethylene copolymer such as EVA using a mixer, a twin screw extruder, or the like, or dissolving the ethylene copolymer A method of adding a cellulosic fiber while stirring the prepared solution can be applied.

  Cellulosic fibers are stable when dispersed in a liquid such as water, but easily aggregate when dried and difficult to redisperse. Therefore, the addition to the ethylene copolymer is preferably carried out in a state where the cellulosic fibers are dispersed in the liquid. In addition, liquids such as water added into the system together with the cellulosic fibers can be removed with a vacuum dryer, etc., but from the productivity and dispersibility of the cellulosic fibers, mixing and dispersion by a twin screw extruder with a vacuum vent, Liquid removal is preferred.

[Molding method]
Although the molding method of a molded object is not specifically limited, For example, well-known molding methods, such as press molding, calendar molding, melt extrusion molding, injection molding, blow molding, are applicable.

  In addition, the molded product of the present embodiment includes an antioxidant, a light stabilizer, a heat retention agent, an antistatic agent, a lubricant, an antiblocking agent, a flame retardant, an antifogging agent, a pigment, a dye, an oil, and a wax as necessary. A foaming agent and the like can be blended in a timely manner.

  Since the molded body according to the present embodiment is excellent in stress crack resistance, for example, it is preferably used for pipes, bottles, bottle caps, and artificial turf that are exposed to stresses such as internal pressure for a long time in contact with various liquids. Can do.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples. The physical property measurement method and evaluation method are as follows.

(1) Measurement of average fiber diameter of cellulosic fibers The fiber diameters of 12 cellulosic fibers arbitrarily selected from images taken using a scanning electron microscope manufactured by Hitachi High Technology Co., Ltd. were measured, and the average was measured. The value was calculated to obtain the average fiber diameter.

(2) Stress crack resistance The stress crack resistance test was conducted by the method described in ASTM D1693. Specifically, a 10% by mass aqueous solution of Liponox NC95 manufactured by Lion Corporation was used as a test solution, and the time at which the probability of cracking due to environmental stress was 50% was measured at 50 ° C.

[Examples 1 to 3]
As an ethylene copolymer, an ethylene-vinyl acetate copolymer (EVA-1: EM-6415 manufactured by Asahi Kasei Chemicals Corporation) having a vinyl acetate content of 14% by mass and MFR = 15 g / 10 min was prepared. Moreover, as a cellulose fiber, it produced by passing the cypress produced in Kagawa Prefecture 16 times through a disk mill and a cellulose fiber (Cell-1) having an average fiber diameter of 50 nm, and passing the cypress through the disk mill 8 times. Cellulosic fibers (Cell-2) having an average fiber diameter of 120 nm were prepared.

  Using the ethylene copolymer and cellulose fiber, pellets were prepared at the ratio shown in Table 1, and a molded sheet was prepared using the pellets, and the stress crack resistance was evaluated. Specifically, an ethylene-vinyl acetate copolymer and an aqueous dispersion slurry of cellulose fibers were mixed using a twin screw extruder, and the strand extruded from the die was cut to produce a pellet. Thereafter, a molded sheet was produced by press molding, and the stress crack resistance was evaluated. Table 1 shows the pellet composition and evaluation results.

[Comparative Examples 1 and 2]
An ultraviolet cut film was prepared by the same operation as in Example 1 except that the blending amount of the cellulosic fiber was changed, and the stress crack resistance was evaluated. Table 1 shows the pellet composition and evaluation results. In Comparative Example 2, the amount of cellulosic fibers was too large, resulting in poor mixing, and the stress crack resistance could not be measured.

[Comparative Example 3]
A UV cut film was prepared by the same operation as in Example 1 except that cellulose fibers (average fiber diameter 11 μm, Cell-3) obtained by defibrating copy paper with a mixer were used as the cellulose fibers, and stress cracking resistance was prevented. Sex was evaluated. Table 1 shows the pellet composition and evaluation results.

  The molded body of the present invention has industrial applicability as a pipe, bottle, bottle cap, and artificial turf.

Claims (2)

Containing a polymerized unit derived from ethylene and a polymerized unit derived from at least one copolymer compound selected from the group consisting of vinyl esters, unsaturated carboxylic acids, derivatives of vinyl esters, and derivatives of unsaturated carboxylic acids, An ethylene copolymer in which the content of the polymerized units derived from the copolymer compound is 5 to 50% by mass;
Cellulosic fibers having an average fiber diameter of 500 nm or less,
The cellulose fiber is contained in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the ethylene copolymer.
Molded body.   The molded article according to claim 1, wherein the ethylene-based copolymer includes an ethylene-vinyl acetate copolymer.