JP3712091B2 - Polyvinyl alcohol moldings - Google Patents

Description

【００２６】
(*1)ゴム粒子の略号：ゴム粒子の水性エマルジョンの略号
(*2)分散安定剤の種類：
ＳＨ−ＰＶＡ：片末端にメルカプト基を有するＰＶＡ
ＮＭ−ＰＶＡ：無変性ＰＶＡ
ＳＬＳ：ラウリル硫酸エステルナトリウム
(*3)ＤＰ：ＰＶＡの重合度
(*4)ＤＨ：ＰＶＡの鹸化度
(*5)［ＳＨ］：ＰＶＡ中に含まれるメルカプト基の含有量
(*6)モノマーの種類：ゴム成分のモノマー
ｎ−ＢｕＡ：アクリル酸ｎ−ブチル
ＭＭＡ：メタクリル酸メチル
【００２７】
【表２】

【００２８】
(*1)ゴム粒子の略号：ゴム粒子の水性エマルジョンの略号
(*2)グラフトしたＰＶＡの重量比
重量比＝グラフトしたＰＶＡの重量／ゴム成分の重量
【００２９】
【表３】

【００３０】
(*1)ＤＰ：ＰＶＡの重合度
(*2)ＤＨ：ＰＶＡの鹸化度
(*3)コモノマー
ＡＭＰＳ：２−アクリルアミド−２−メチルプロパンスルホン酸ナトリウム
(*4)ゴム粒子の略号：ゴム粒子の水性エマルジョンの略号
(*5)ゴム成分の重量比：ＰＶＡの総重量に対するゴム成分の重量比
(*6)可塑剤の添加量：ＰＶＡの総重量に対する重量比
【００３１】
【表４】

【００３２】
(*1)耐衝撃性：低温低湿度下（５℃，４０％ＲＨ）における耐衝撃性
評価結果を下記の記号で示す。
◎：非常に優れている
○：優れている
△：悪い
×：非常に悪い
数値は落下試験に供したサンプル１０個のうち破袋しなかったサンプル数を示す。
(*2)強伸度：高湿度下（２０℃，８４％ＲＨ）における力学的物性
(*3)フィルムの透明性：フィルムの外観の指標
顔料を添加しないでフィルムの透明性を観察し、その評価結果を下記の記号で示す。
◎：透明
△：やや濁っている
×：白濁
(*4)総合評価
低温低湿における耐衝撃性、高湿度下における強伸度および外観を総合的に評価した結果を下記の記号で示す。
◎：非常に優れている
○：優れている
△：悪い
×：非常に悪い
(*5)：ゴム粒子が凝集し、均一なフィルムを得ることができなかった。
【００３３】
【発明の効果】
本発明の成形物は低温・低湿度下において高い衝撃強度を有すると共に、高湿度下においても高い強度，ヤング率を有しており、外観も良好である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyvinyl alcohol-based molded article having improved impact strength at low temperatures and low humidity and excellent appearance.
[0002]
[Prior art]
Polyvinyl alcohol polymers (hereinafter abbreviated as PVA) are excellent in high gas barrier properties, transparency, oil resistance, water solubility, strength, etc., and are widely used as packaging materials and containers for films and bottles. Have been used.
[0003]
However, since a film made of PVA is hard and brittle at low temperatures and low humidity, it has a problem that its strength against impact is remarkably low. For this reason, the packaging material and container which used PVA were torn or cracked during conveyance and transportation, and there existed a problem that the content leaked. On the other hand, it is possible to improve the property of being hard and brittle under low temperature and low humidity by blending PVA with a material called a plasticizer such as a polyhydric alcohol such as glycerin or ethylene glycol or a derivative thereof. Has been tried. However, this method cannot sufficiently improve the impact resistance at low temperatures and low humidity. If a large amount of plasticizer is added, the strength and elasticity under high humidity are reduced, and the films adhere to each other. Then there was a problem such as blocking.
In recent years, for polymers such as polystyrene and polyacrylate, a method for improving impact resistance by dispersing a rubber component in a polymer matrix has been attempted. However, in the case of PVA, the rubber particles are not uniformly dispersed in the polymer matrix, and it is difficult to contain a rubber component in an amount effective for impact resistance. There was a problem that was damaged.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a PVA-based molded article having high strength and elasticity under high humidity, high impact strength even under low temperature and low humidity, and excellent in appearance.
[0005]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the inventors of the present invention are polyvinyl alcohol-based molded products comprising a polyvinyl alcohol-based polymer (A) and rubber particles (B), and the rubber particles (B) have a glass transition. A rubber component having a temperature of 5 ° C. or less and an average particle size of 5 μm or less and a polyvinyl alcohol polymer (C) bonded to the surface thereof, and the weight of the rubber component in the rubber particles (B) with respect to the total weight of the polyvinyl alcohol polymer A polyvinyl alcohol-based molded product having a composition ratio in the range of 0.03 to 2 has been found and the present invention has been completed.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The PVA molded product of the present invention is a molded product composed of PVA (A) and rubber particles (B). Among the PVA molded products of the present invention, it is preferable that PVA (A) is a continuous layer and rubber particles (B) are distributed in islands in the continuous layer.
[0007]
PVA (A) used in the present invention is a polymer having vinyl alcohol units.
The viscosity average polymerization degree of PVA (hereinafter abbreviated as polymerization degree) is preferably 200 to 18000. In the case of melt molding, the polymerization degree of PVA is preferably 300 to 2000. In the case of molding from a solution, the polymerization degree of PVA is preferably 1000 to 8000. Degree of polymerization and decreases the strength of the molded product with a low over-Gill, polymerization degree is too high solution or melt viscosity becomes formability is deteriorated high.
The saponification degree of PVA is preferably 50 mol% or more, more preferably 65 mol% or more, and particularly preferably 70 mol% or more. In consideration of compatibility with rubber particles and plasticizer, the saponification degree of PVA is most preferably 80 to 100 mol%. If the degree of saponification is too low, it becomes soft at high temperatures or high humidity, and the strength and elastic modulus decrease, and it becomes hard and brittle at low temperatures.
[0008]
Although there is no restriction | limiting in particular in the manufacturing method of PVA, Generally, it manufactures by the hydrolysis or alcoholysis of polyvinyl ester. Polyvinyl esters include homopolymers of vinyl esters, copolymers of two or more vinyl esters, and copolymers of vinyl esters and other ethylenically unsaturated monomers. Here, examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl versatate, vinyl pivalate, etc. Among them, industrially inexpensive vinyl acetate is generally used.
The PVA used in the present invention may be copolymerized with other monomers, and those obtained by modifying the terminal of the polymer using a chain transfer agent can also be used. The ethylenically unsaturated monomer copolymerized with the vinyl ester is not particularly limited as long as it is copolymerizable with the vinyl ester, and α-olefin, halogen-containing monomer, carboxylic acid-containing monomer, and the like Anhydride or its ester, (meth) acrylic acid ester, vinyl ether, sulfonic acid group-containing monomer, amide group-containing monomer, amino group-containing monomer, quaternary ammonium base-containing monomer, silyl group-containing Monomers, hydroxyl group-containing monomers, acetyl group-containing monomers and the like can be mentioned.
Examples of the polymerization method include solution polymerization, bulk polymerization, pearl polymerization, and emulsion polymerization.
[0009]
The rubber particles (B) used in the present invention must have PVA (C) bonded to the surface of the rubber component. The bond between the rubber component and PVA (C) may be a bond as long as the rubber particles do not aggregate when PVA (A), which is a matrix in the molded article, is dissolved in water, and a chemical bond is preferable. Graft bonds are more preferred. The polymerization degree and saponification degree of PVA (C) bonded to the surface of the rubber component are preferably selected in consideration of the compatibility of the matrix with PVA (A) and the ease of bonding with the rubber component. .
The weight ratio of PVA (C) to the rubber component is preferably 0.005 or more, more preferably 0.02 or more, more preferably 1 to 50, and particularly preferably 1 to 30. The weight ratio is appropriately set depending on the particle diameter of the rubber particles, the composition of the rubber component, and the weight ratio of the rubber component in the molded product.
The rubber particles (B) can be produced by reacting the rubber component and PVA under melt kneading, pulverizing the micro-dispersed rubber component in PVA, and forming the rubber component. Examples thereof include a method of bonding PVA to the surface and a method of emulsion polymerization of a rubber component using PVA as a dispersion stabilizer. Among these, a method of emulsion polymerization of rubber component PVA as a dispersion stabilizer is preferred.
Among emulsion polymerizations, the method of emulsion polymerization of a rubber component using a PVA containing a mercapto group as a dispersion stabilizer is most suitable for bonding PVA to the surface of the rubber component, and a rubber having a high PVA graft ratio. Particles can be obtained.
[0011]
50-3000 are preferable and, as for the polymerization degree of PVA containing a mercapto group, 100-2000 are more preferable. The saponification degree of the PVA containing a mercapto group is preferably in the range of water solubility or water dispersibility, preferably 60 to 100 mol%, more preferably 75 to 100 mol%.
The position of the mercapto group present in PVA may be the terminal or side chain of PVA, but one terminal is particularly preferred.
Examples of the method for producing a PVA containing a mercapto group include the method described in JP-A No. 59-187003.
The PVA containing a mercapto group may be copolymerized with a copolymerizable ethylenically unsaturated monomer unit other than vinyl alcohol units and vinyl acetate units within the range not impairing the characteristics of the present invention.
[0012]
As the dispersion stabilizer used for emulsion polymerization, PVA containing a mercapto group may be used alone or in combination with other dispersion stabilizers. Examples of the dispersion stabilizer that can be used in combination include various anionic, cationic, and nonionic surfactants used in emulsion polymerization or various water-soluble polymers.
[0013]
The rubber particles obtained by emulsion polymerization of a rubber component using a PVA polymer containing a mercapto group as a dispersion stabilizer will be described in more detail.
Examples of the emulsion polymerization method include a method of homopolymerizing or copolymerizing a radically polymerizable ethylenically unsaturated monomer or diene monomer (JP-A-60-197229).
As a polymerization initiator used for emulsion polymerization, water-soluble such as potassium bromate, potassium persulfate, ammonium persulfate, 2,2-azobis (2-amidinopropane) hydrochloride, azobiscyanovaleric acid, t-butyl hydroperoxide, etc. Initiators are mentioned.
Examples of the ethylenically unsaturated monomer or diene unsaturated monomer used as the rubber component monomer include vinyl ester monomers, α-olefins, halogen-containing monomers, carboxylic acid-containing monomers, and the like. Its anhydride or ester, (meth) acrylic acid ester, vinyl ether, sulfonic acid group-containing monomer, amide group-containing monomer, amino group-containing monomer, quaternary ammonium base-containing monomer, silyl group-containing Examples thereof include ethylenically unsaturated monomers such as monomers, hydroxyl group-containing monomers, and acetyl group-containing monomers. Among these, (meth) acrylic acid ester monomers are preferable.
[0014]
The glass transition temperature (Tg) of the rubber component is 5 ° C. or less, preferably −5 ° C. or less, particularly preferably −15 ° C. or less. A preferable lower limit of the glass transition temperature is about −100 ° C. When the glass transition temperature is higher than 5 ° C., the impact resistance at low temperatures becomes insufficient, and the molded product becomes brittle and causes problems such as cracking.
Examples of the method of setting the glass transition temperature of the rubber component to 5 ° C. or less include a method of adjusting the composition of the rubber component and adding a plasticizer to the rubber component.
The rubber particles thus obtained may be used as an aqueous dispersion, or may be dried or concentrated.
[0015]
The average particle size of the rubber particles of the present invention is 5 μm or less, preferably 1 μm or less, particularly preferably 0.8 μm or less. The lower limit of the average particle diameter is preferably 0.005 μm, more preferably 0.01 μm. When the average particle size is larger than 5 μm, sufficient impact resistance cannot be obtained.
[0016]
In the molded product of the present invention, the weight ratio of the rubber component to the total weight of PVA [total amount of PVA (A) and PVA (C)] is 0.03 to 2, preferably 0.05 to 1.5. 0.1 to 1 is more preferable, and 0.15 to 1 is most preferable. When the weight ratio is less than 0.03, the impact resistance is not sufficiently exhibited. On the other hand, when the weight ratio is larger than 2, the strength and elongation of the molded product are lowered.
[0017]
As a method of blending the rubber particles (B) in the PVA (A), a method in which the rubber particles are previously added to the PVA is molded [hereinafter abbreviated as a method (A)]. A method of adding [hereinafter abbreviated as method (B)], a method of immersing a molded product of PVA in a rubber particle dispersion and impregnating the molded product with rubber particles [hereinafter abbreviated as method (C)]. Can be mentioned. Among these methods, the method (A) and the method (B) are preferable. The method (A) includes a method of molding from a mixed solution of PVA and rubber particles. The method (B) includes adding and blending rubber particles while extruding an aqueous PVA solution using an apparatus comprising an extruder. A method is mentioned.
[0018]
In the molded product of the present invention, the plasticizer for PVA is added in a weight ratio range of 0.01 to 1 with respect to the total weight of PVA [total amount of PVA (A) and PVA (C)]. Is preferable, 0.03-1 is more preferable, and 0.05-0.8 is particularly preferable.
The plasticizer may be any substance that lowers the glass transition temperature of PVA, such as water, ethylene glycol and oligomers thereof, polyethylene glycol, propylene glycol and oligomers thereof, glycol derivatives such as polypropylene glycol, glycerin and oligomers thereof, poly Examples thereof include glycerin derivatives obtained by adding ethylene oxide, propylene oxide and the like to glycerin and glycerin, and sorbitol derivatives obtained by adding ethylene oxide, propylene oxide and the like to sorbitol and sorbitol. Among these, polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, sorbitol and their derivatives are preferably used.
These plasticizers may be used alone or several plasticizers may be used in combination.
[0019]
As the molding method of the molded product of the present invention, various molding methods such as melt molding, injection molding, press molding, and molding from a solution are possible.
After, prepare PVA solution, as a method for forming the film include the following methods.
As the solvent used in the steel tone PVA solution, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N- methylpyrrolidone, ethylene glycol, propylene glycol, glycerine, ethylene diamine, is used diethylenetriamine, and water or the like, alone or in combination . An aqueous solution of an inorganic salt such as lithium chloride or calcium chloride may be used alone or in combination with the organic solvent. Among these, water alone, a mixed solvent of dimethyl sulfoxide or dimethylformamide and water, or a glycol solvent such as glycerin is preferably used. The concentration of the PVA solution varies depending on the polymerization degree of PVA and the film forming method, but is usually 1 to 95% by weight, preferably 1.5 to 60% by weight. PVA solution is typically manufactured by regulated at a temperature of room temperature to 150 DEG ° C.. In this case, depending on the solvent used, to avoid the lowering of polymerization degree due to decomposition of PVA, it is preferable to made tone at lower temperatures within the above range.
[0020]
Examples of film forming methods include cast film formation from a PVA solution, dry film formation by extrusion into an inert gas such as air or nitrogen, and melt molding. Moreover, the wet film formation by the extrusion from the PVA solution in the poor solvent can also be performed. Further, a dry / wet film forming method in which a PVA solution is once extruded into air or an inert gas such as nitrogen to form a liquid film and then introduced into a coagulation bath to form a film is possible. Furthermore, it is possible to combine these film forming methods, and to form a film from a film obtained by cooling and gelling a liquid film to be produced.
Cast film formation or dry film formation, which is a general film formation method of PVA, is a method in which a PVA solution is cast on a rotating drum or endless belt to form a liquid film, which is then dried to remove the solvent. It is.
[0021]
The molded article of the present invention is used in the fields of textiles, clothing, electronic materials, medical / biochemical waste packaging, various packaging materials such as detergents, chemicals, agricultural chemicals, dyes, and containers. The molded product of the present invention may be treated by mixing additives, modifiers, fillers, etc., surface treatment, etc., as long as the characteristics of the present invention are not impaired.
[0022]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not restrict | limited at all by an Example. In the following description, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
[0023]
Various physical properties were evaluated according to the following methods.
(1) Glass transition temperature The glass transition temperature (hereinafter abbreviated as Tg) of the rubber component was calculated from the copolymer composition based on the following Fox formula.
1 / Tg = Σ (Wi / Tgi) (Fox equation)
Here, Wi and Tgi are the weight fraction and Tg of component i, respectively.
As the Tg of each component, a value described in Polymer Hand Book (John Wiley & Sons Inc) was used.
Σ means that the components are added together.
(2) The impact resistant film (width 10 cm, length 20 cm, thickness 0.05 mm) was folded, and the two pieces were heat sealed to form a bag (width 10 cm, length 10 cm). The obtained bag was filled with Toyoura standard sand, and then the opening was heat-sealed to prepare a package for evaluation.
The package was allowed to stand for 7 days in an environment of 5 ° C. and 40% RH, and was then subjected to humidity control. Then, the package was dropped from a position of 2 m onto a stainless steel plate having a thickness of 8 mm. The state of the package after dropping was observed.
(3) Strength and elongation of the film, Young's modulus A sample film (width 10 mm, thickness 0.05 mm) was allowed to stand for 7 days in an environment of 20 ° C. and 84% RH, and then the humidity was adjusted. The maximum strength, elongation at break, and Young's modulus when stretched at a rate of min were measured.
(4) Average particle size The particle size of an aqueous dispersion of rubber particles synthesized by emulsion polymerization was measured with a particle size distribution meter (manufactured by Otsuka Electronics Co., Ltd., model: ELS-800).
(5) Graft ratio of PVA to rubber component Measured according to the method of Otsuka et al. (Otsuka, Fujii, Polymer Chemistry, 25, 375 (1968)). That is, rubber particles are dispersed in ion exchange water, and the particles are separated by centrifugation. The PVA concentration in the supernatant was quantified by a colorimetric method (method for measuring the color density of PVA by iodine). The amount of PVA grafted to the rubber component was calculated from the amount of PVA used during emulsion polymerization and the amount of PVA in the supernatant.
(6) Binding amount of PVA to rubber component After the matrix of the molded product was dissolved in water, the rubber particles were separated from the aqueous solution by centrifugation. After sufficiently washing the separated rubber particles with water, periodic acid was added to the rubber particles to cut the PVA bonded to the rubber component, and the separated PVA was quantified by a known method.
[0024]
Examples 1-9, Comparative Examples 1-8
(1) carried out emulsion polymerization by methods known in the compositions shown in tone made <br/> Table 1 of an aqueous emulsion of the rubber particles to obtain an aqueous emulsion. The initiator was potassium persulfate, the monomers were charged all at once, and the polymerization temperature was 70 ° C. Table 2 shows the physical properties of the obtained emulsion.
(2) compositions shown in tone made <br/> Table 3 of the film so that (in terms of solid content), PVA, an aqueous emulsion and a concentration of 10% aqueous solution containing a plasticizer of the rubber particles was made tone, A liquid film was formed by casting on a polyester film.
The liquid film was dried at 70 ° C. for 1 hour, and further heat-treated at 120 ° C. for 10 minutes to obtain a film. Table 4 shows the physical properties of the film.
[0025]
[Table 1]

[0026]
(* 1) Abbreviation for rubber particles: Abbreviation for aqueous emulsion of rubber particles
(* 2) Type of dispersion stabilizer:
SH-PVA: PVA having a mercapto group at one end
NM-PVA: Unmodified PVA
SLS: Sodium lauryl sulfate ester
(* 3) DP: Degree of polymerization of PVA
(* 4) DH: Saponification degree of PVA
(* 5) [SH]: Mercapto group content in PVA
(* 6) Type of monomer: Rubber component monomer n-BuA: n-butyl acrylate MMA: methyl methacrylate
[Table 2]

[0028]
(* 1) Abbreviation for rubber particles: Abbreviation for aqueous emulsion of rubber particles
(* 2) Weight ratio of grafted PVA Weight ratio = Weight of grafted PVA / Weight of rubber component
[Table 3]

[0030]
(* 1) DP: Degree of polymerization of PVA
(* 2) DH: Saponification degree of PVA
(* 3) Comonomer AMPS: Sodium 2-acrylamido-2-methylpropanesulfonate
(* 4) Abbreviation for rubber particles: Abbreviation for aqueous emulsion of rubber particles.
(* 5) Weight ratio of rubber component: Weight ratio of rubber component to the total weight of PVA
(* 6) Amount of plasticizer added: Weight ratio to the total weight of PVA [0031]
[Table 4]

[0032]
(* 1) Impact resistance: Impact resistance evaluation results at low temperature and low humidity (5 ° C, 40% RH) are indicated by the following symbols.
A: Very good B: Excellent B: Bad x: A very bad number indicates the number of samples not broken in 10 samples subjected to the drop test.
(* 2) High elongation: Mechanical properties under high humidity (20 ℃, 84% RH)
(* 3) Transparency of the film: The transparency of the film is observed without adding an indicator pigment for the appearance of the film, and the evaluation results are indicated by the following symbols.
◎: Transparent △: Slightly cloudy ×: Cloudy
(* 4) Comprehensive evaluation The following symbols indicate the results of comprehensive evaluation of impact resistance at low temperature and low humidity, strength and elongation at high humidity, and appearance.
◎: Very good ○: Excellent △: Bad ×: Very bad
(* 5): Rubber particles aggregated and a uniform film could not be obtained.
[0033]
【The invention's effect】
The molded product of the present invention has high impact strength at low temperatures and low humidity, high strength and Young's modulus even under high humidity, and good appearance.

Claims (2)

A polyvinyl alcohol-based molded article comprising a polyvinyl alcohol-based polymer (A) and rubber particles (B), the rubber particles (B) having a rubber component having a glass transition temperature of 5 ° C. or less and an average particle size of 5 μm or less on the surface thereof A polyvinyl alcohol-based molded article comprising a bonded polyvinyl alcohol-based polymer (C), wherein the weight composition ratio of the rubber component in the rubber particles (B) to the total weight of the polyvinyl alcohol-based polymer is in the range of 0.03 to 2. . The polyvinyl alcohol-based molded article according to claim 1, comprising a plasticizer for a polyvinyl alcohol-based polymer in a weight composition ratio of 0.01 to 1 with respect to the total weight of the polyvinyl alcohol-based polymer.