JPH06192523A - Vinylidene chloride copolymer composition - Google Patents

Abstract

PURPOSE:To provide a vinylidene chloride copolymer composition having excellent thermal stability and free from food sanitation problem. CONSTITUTION:The vinylidene chloride polymer composition contains (A) 100 pts.wt. of a vinylidene chloride copolymer, (B) 0.05-4 pts.wt. of an epoxy-based stabilizer, (C) 0.01-3 pts.wt. of at least one kind of alkali metal citrate selected from sodium citrate and potassium citrate and (D) 0.1-10 pts.wt. of a plasticizer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinylidene chloride copolymer composition, more specifically, it has excellent thermal stability.
The present invention relates to a vinylidene chloride-based copolymer composition having no food hygiene problem. The vinylidene chloride copolymer composition of the present invention can be used as a raw material for various molded products, and is particularly suitable for producing a food packaging film by extrusion molding.

[0002]

BACKGROUND OF THE INVENTION Vinylidene chloride copolymer films are
Since it is a transparent film with excellent oxygen gas barrier properties and moisture resistance, it can be used as a packaging material for commercial or household wrap films and other foods, such as fresh fish, raw meat, fresh vegetables, prepared foods, etc. It is widely used for the purpose of preventing moisture.

A vinylidene chloride homopolymer is easily crystallized and has a high softening point, and since it has a chlorine content higher than that of vinyl chloride, the softening point and the decomposition temperature (dehydrochlorination reaction) are close to each other. It has a drawback of poor extrusion processability.
Therefore, vinylidene chloride is usually copolymerized with vinyl chloride and other monomers to form a vinylidene chloride-based copolymer, and by adding a plasticizer and a stabilizer to the copolymer, the extrusion processability is improved. is doing. Therefore, a vinylidene chloride-based copolymer film is generally formed by melt-extruding a composition in which various additives such as a stabilizer and a plasticizer are added to a vinylidene chloride-based copolymer, and then forming the film by an inflation method or the like. Is manufactured by.

In order for the vinylidene chloride copolymer film to retain good commercial value, it is less affected by decomposition or discoloration due to heat during molding, and
For food packaging, there should be no food hygiene issues.

Conventionally, as a vinylidene chloride copolymer composition used for food packaging materials, a vinylidene chloride copolymer is added to an epoxy stabilizer such as epoxidized vegetable oil and a plasticizer such as glycerin ester or dibutyl sebacate. A mixture of agents is known (for example, Japanese Patent Publication No.
9-46984). However, the conventionally known vinylidene chloride-based copolymer composition is not yet sufficiently satisfactory in terms of thermal stability, and there are problems such as dehydrochlorination reaction and discoloration during heating, and therefore its solution is urgent. It is peeling.

On the other hand, it is known to use citric acid, citric acid salts, citric acid esters and the like as stabilizers for vinyl chloride polymers. For example, JP-A-59-8045
Japanese Patent No. 6 discloses a composition obtained by adding a heat stabilizing system containing sodium or potassium citrate and organic tin or antimony to a vinyl chloride polymer. JP-A-59-108054 discloses a composition in which barium carbonate or cadmium carbonate particles and sodium citrate, potassium citrate, or a metal salt of phosphoric acid are used in combination and added to a vinyl chloride polymer. There is. However, these known stabilizer systems contain components such as organic tin, organic antimony, and cadmium carbonate, which are problematic for food hygiene.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a vinylidene chloride-based copolymer composition which is excellent in heat stability and has no food hygiene problems. As a result of intensive studies to overcome the above-mentioned problems of the prior art, the present inventors have found that a vinylidene chloride copolymer contains a plasticizer, an epoxy stabilizer and sodium citrate and / or potassium citrate in a specific ratio. It was found that the thermal stability was remarkably improved and there was no problem in food hygiene by adding them together.

The present inventors have found that various stabilizers such as various phenolic antioxidants, metallic soaps, calcium hydroxide, sodium hydroxide, ethylenediaminetetraacetic acid metal salt and sodium pyrophosphate are vinylidene chloride copolymers. The effect of heat stabilization was investigated, and among them, it was found that sodium citrate and potassium citrate exhibited excellent effects. Moreover, among citric acid compounds such as citric acid, citric acid salts, and citric acid esters, sodium citrate and potassium citrate show particularly excellent effects, and when combined with an epoxy stabilizer and a plasticizer, chloride It has been found that a vinylidene-based copolymer can be provided with a remarkable heat stabilizing effect.
These sodium citrate and potassium citrate are also used as food additives and have no food hygiene problems.

Since the vinylidene chloride copolymer composition of the present invention is excellent in extrusion processability, it can be used to produce a food packaging film or various molded products, fibers, etc. by extrusion process. The present invention has been completed based on these findings.

[0010]

Thus, according to the present invention, 100 parts by weight of (A) a vinylidene chloride copolymer,
(B) 0.05 to 4 parts by weight of epoxy stabilizer, (C) at least one alkali metal citrate selected from the group consisting of sodium citrate and potassium citrate.
A vinylidene chloride-based copolymer composition is provided, which comprises 0.1 to 3 parts by weight of (D) and 0.1 to 10 parts by weight of a plasticizer (D).

The present invention will be described in detail below. The vinylidene chloride copolymer used in the present invention is vinylidene chloride 7
It is a copolymer composed of 0 to 96% by weight and 4 to 30% by weight of a copolymerizable monomer. Examples of the monomer copolymerizable with vinylidene chloride include vinyl chloride, acrylonitrile, acrylic acid, acrylic acid alkyl ester (alkyl group having 1 to 18 carbon atoms), methacrylic acid, methacrylic acid alkyl ester (alkyl group carbon atom). 1 to 18), maleic anhydride, maleic acid, maleic acid alkyl ester, itaconic acid alkyl ester, vinyl acetate, ethylene, propylene, isobutylene, butadiene and the like. If the content of vinylidene chloride is less than 70% by weight, the gas barrier properties against oxygen, water vapor, etc. are deteriorated. On the other hand, if it exceeds 96% by weight, the melting point becomes too high, and thermal decomposition tends to occur during melt molding.

The reduced viscosity is an index showing the molecular weight of the polymer, and the reduced viscosity measured at 30 ° C. at a concentration of 4 g / liter (g / L) using cyclohexanone as a solvent is usually 0.035 to 0. 080 L / g, preferably in the range of 0.038 to 0.065 L / g is desirable. If the reduced viscosity is lower than 0.035 L / g, the molding process is difficult because the molecular weight is too low.
If it exceeds L / g, the molecular weight becomes too high and melt processing becomes difficult.

The epoxy stabilizer used in the present invention is a compound having an epoxy group in the molecule, which is usually used as a heat stabilizer for vinylidene chloride copolymers. The epoxy-based stabilizer acts as a scavenger of hydrogen chloride generated by thermal decomposition of the vinylidene chloride-based copolymer.

Examples of the epoxy-based stabilizer include epoxidized vegetable oil obtained by epoxidizing linseed oil, soybean oil, coconut oil, safflower oil, sunflower oil, cottonseed oil, sunflower oil, etc .; epoxidized octyl stearate. Epoxidized fatty acid monoester; epoxidized fatty acid diester obtained by epoxidizing unsaturated fatty acid glycol ester; alicyclic epoxide represented by epoxy hexahydrophthalic acid ester; and the like. Among these, epoxidized vegetable oil is particularly preferable from the viewpoint of food hygiene.

The mixing ratio of the epoxy stabilizer is 0.05 to 4 with respect to 100 parts by weight of the vinylidene chloride copolymer.
Parts by weight, preferably 0.3 to 3 parts by weight, more preferably 0.5 to 2 parts by weight. If the blending ratio is too low, the heat stabilizing effect is small even when used in combination with sodium citrate and / or potassium citrate, and conversely, if the blending ratio is too high, the composition is colored or the film-forming property is impaired. Or the gas barrier property may deteriorate.

The alkali metal citrate used in the present invention is at least one selected from the group consisting of sodium citrate and potassium citrate. As sodium citrate, there are trisodium citrate (crystal) and trisodium citrate (anhydrous), and trisodium citrate (crystal) is particularly preferable. The potassium citrate used in the present invention is 1 potassium citrate and 3 potassium citrate, and 3 potassium citrate is particularly preferable. These alkali metal citrates are colorless crystals or white powders. Sodium citrate and potassium citrate may be used alone or in combination.

The mixing ratio of the alkali metal citrate is 0.0 to 100 parts by weight of the vinylidene chloride copolymer.
It is 1 to 3 parts by weight, preferably 0.1 to 2 parts by weight, and more preferably 0.3 to 1 part by weight. If this blending ratio is too small, the heat stabilizing effect will be small even when used in combination with an epoxy stabilizer. Conversely, if it is too large, the composition will be colored, the film-forming property will be impaired, or the gas barrier will be impaired. May deteriorate.

The total amount of the epoxy stabilizer and alkali metal citrate used is preferably 5 parts by weight or less, more preferably 4 parts by weight or less, based on 100 parts by weight of the vinylidene chloride copolymer. Is desirable. If the amount of these stabilizer components used is too large, the composition may be colored. Further, the epoxy stabilizer and the alkali metal citrate are used in a weight ratio of 5: 5 to 9.
The range of 5: 0.5 is preferable for achieving the combined effect of both.

The plasticizer used in the present invention is not particularly limited as long as it is a plasticizer used in the usual molding and processing of vinylidene chloride copolymers. Specific examples of the plasticizer include
Aliphatic dibasic acid esters such as dioctyl adipate, dioctyl sebacate and dibutyl sebacate; hydroxy polycarboxylic acid esters such as tributyl citrate and tributyl acetyl citrate; Ester plasticizers; polyester plasticizers and the like can be exemplified.

The mixing ratio of the plasticizer is 0.1 to 10 parts by weight, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the vinylidene chloride copolymer. If it is less than 0.1 part by weight, the molding process is difficult.
Performance such as gas barrier properties may be impaired.

The vinylidene chloride copolymer composition of the present invention is prepared by treating each component by a conventional method, for example, a ribbon blender,
It can be prepared by mixing using a Henschel mixer, a kneader or the like. Further, an epoxy stabilizer, an alkali metal citrate salt, and a plasticizer may be appropriately added and mixed in a step during or after the polymerization of the vinylidene chloride copolymer. A preferred mixing method is a method in which an alkali metal citrate is dissolved in water, alcohol, acetone or the like, and the resulting solution is mixed with a vinylidene chloride copolymer, an epoxy stabilizer, and a plasticizer using a mixer. is there.

The composition of the present invention comprises, as far as the object of the present invention is not impaired, colorants such as dyes or pigments known as additives for food packaging materials, stabilizers such as antioxidants, and weather resistance improvers. Inorganic powders such as silica, lubricants, nucleating agents, MBS resins and the like can be added.

The composition of the present invention can be formed into a molded product such as a film, a sheet, a container or a fiber by a usual melt molding. In the case of producing a film, for example, the composition is melt extruded from a circular die of an extruder, the obtained tubular product is passed through a first bath at room temperature or lower, and then a second 5 ° C.
A stretched film can be produced by an inflation method in which a bubble is blown between two sets of pinch rollers by passing through a bath at about 50 ° C. The composition can also be melt extruded through a T-die of an extruder and rapidly cooled to form a sheet or film. A fiber can be obtained by extruding the melt in a linear shape and stretching the melt in a uniaxial direction.

[0024]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The addition amount is parts by weight.

[Example 1, Comparative Examples 1 to 3] Vinylidene chloride copolymer (reduced viscosity: 0.058 L / g) [P of 80% by weight of vinylidene chloride and 20% by weight of vinyl chloride] [P
VDC (1)] 100 parts by weight of epoxidized soybean oil in the amount shown in Table 1 and sodium citrate dissolved in warm water in an amount twice that of sodium citrate (Na citrate; crystals) in Table 1 The hot water solution and the amount of dibutyl sebacate (DBS) shown in Table 1 were added and mixed using a Henschel mixer until the temperature of the resin reached 70 ° C. After cooling, the obtained composition was pressed at 165 ° C. for 3 minutes to prepare a sheet having a thickness of about 0.5 mm.

<Reduced viscosity> The reduced viscosity of the vinylidene chloride-based copolymer was measured by the following method. 80 mg of the dried polymer was weighed in an Erlenmeyer flask with a stopper, 20 ml of cyclohexanone at 30 ° C. was added, and the mixture was stirred in a water bath at 70 ° C. for 1 hour. Then, the obtained solution was placed in an Ubbelohde viscometer, and the dropping time (seconds) was measured in a constant temperature water bath adjusted to 30 ° C., and calculated by the following formula. Reduced viscosity (ηsp / c) = 1 / C [(t ₂ / t ₁ ) −1] C: Concentration (4 g / L) t ₁ : Drop time (seconds) of cyclohexanone at 30 ° C. t ₂ : Polymer 30 ° C of dissolved cyclohexanone solution
Fall time (in seconds)

<Thermal Colorimetric Value> 2 cm in length from the above sheet,
Cut 9 samples of 4cm in width, put them in a hot air dryer adjusted to 155 ° C, take out one sample every 15 minutes, and measure the degree of discoloration with the naked eye and a color difference meter (Minolta Co., CR -200) L ^* , a ^* ,
Evaluation was made by measuring the b ^* value. The results are shown in Table 1.
L ^* means lightness, and a ^* and b ^* mean chromaticity representing hue and saturation. L ^* indicates a direction in which the brightness increases (whitens) as the numerical value increases, and the darkness increases (blackens) as the numerical value decreases. a ^* indicates a direction in which the reddishness becomes stronger as the plus value becomes larger, and the greenness becomes stronger as the minus value becomes larger. b ^* is
The larger the plus value, the stronger the yellowishness, and the larger the negative value, the stronger the bluishness.

[0028]

[Table 1] (Footnote) The addition amount in the prescription column is parts by weight.

Example 1 shows that the degree of decrease in L ^* value is smaller than that of Comparative Examples 1 to 3 and, as can be seen from the change in color tone with the naked eye, there is less discoloration due to heat deterioration or the like. It can be seen that the heat stabilization effect is excellent.

Example 2, Comparative Example 4 As a vinylidene chloride-based copolymer, a copolymer of 95% by weight of vinylidene chloride and 5% by weight of methyl acrylate (reduced viscosity:
039 L / g) [PVDC (2)] was used, a sample was prepared in the same manner as in Example 1 and Comparative Example 3, and the degree of discoloration was measured in the same manner. The results are shown in Table 2.

[0031]

[Table 2] (Footnote) The addition amount in the prescription column is parts by weight.

Example 2 shows less discoloration than Comparative Example 4, as is clear from the degree of decrease in L ^* value and the change in color tone with the naked eye. The present invention shows that a composition using a vinylidene chloride-methyl acrylate copolymer as the vinylidene chloride-based copolymer also has an excellent heat stabilizing effect.

[Examples 3 to 4, Comparative Examples 5 to 14] The vinylidene chloride copolymer [PVDC used in Example 1
Each component shown in Tables 3 and 4 was added to (1)] and mixed in the same manner as in Example 1. After cooling, the resulting formulation is
The sheet was pressed at 0 ° C. for 3 minutes to prepare a sheet similar to that in Example 1, and then the degree of discoloration was measured by a color difference meter (CR-200 manufactured by Minolta Co., Ltd.). The results are shown in Table 3.
And 4 are shown.

[0034]

[Table 3] (Footnote) The addition amount in the prescription column is parts by weight.

[0035]

[Table 4] (Footnote) The addition amount in the prescription column is parts by weight. (* 1): 2,6-di-tert-butyl paracresol (* 2): triethylene glycol bis [3- (3-t
-Butyl-5-methyl-4-hydroxyphenyl) propionate] (* 3): sodium pyrophosphate (* 4): distearyl-3,3'-thiodipropionate (* 5): tocopherol

It can be seen that sodium citrate has a smaller degree of decrease in L ^* value than conventional stabilizers and other citric acid compounds, and has an excellent heat stabilizing effect.

[Examples 5 to 6 and Comparative Example 15] Vinylidene chloride copolymer (88% by weight of vinylidene chloride and 12% by weight of vinyl chloride) (reduced viscosity: 0.059 L / g)
[PVDC (3)] 30 kg of epoxidized linseed oil in a blending ratio shown in Table 5, sodium citrate hot water solution dissolved in the same amount of hot water as the weight of sodium citrate in Table 5, And DBS were added and mixed at 70 ° C. using a vane blender, and then cooled to prepare each film-forming compound. The water content of each of these compounds was 0.05% or less.

Then, the compound thus obtained was used as barrel temperature 127 ° C./147° C./16
It was obtained by melt extrusion using an extruder (caliber = 40 mm, L / D = 22, annular nozzle = 24.0 × 25.5 mm) set to 8 ° C./170° C. and a nozzle part temperature of 167 ° C. The parison was cooled while being taken up by a pinch roller placed in cooling water at 6 ° C. afterwards,
Pass a second bath at 25 ° C., insert compressed air into the parison between two pairs of pinch rollers at room temperature, and stretch 3.2 times in the length direction and 3.8 times in the width direction by the inflation method, The biaxially stretched film having a film thickness of 40 μm and a folding width of 80 mm was manufactured by winding 100 m around a 3-inch paper tube.

In order to see the effect of heat stabilization, 5 samples of 2 cm in length and 5 cm in width were prepared from the flat parison before inflation and placed in a hot air dryer adjusted to 150 ° C. for 60 minutes or 75 minutes. , 90 minutes, 105 minutes, one sample was taken out, and the L ^* value was measured by a color difference meter (CR-200 manufactured by Minolta). Further, the color tone of the winding appearance of the stretched film wound around the paper tube was visually judged. The results are shown in Table 5.

[0040]

[Table 5] (Footnote) The addition amount in the prescription column is parts by weight.

[Examples 7 to 8 and Comparative Examples 16 to 17] The vinylidene chloride copolymer [PVDC used in Example 1 was used.
(1)] With respect to 100 parts by weight, the amount of epoxidized soybean oil shown in Table 6 and 3 potassium citrate as potassium citrate (K citrate) were used. A solution of K citrate in warm water dissolved in warm water, DBS and tributyl acetyl citrate (ATBC) in the amounts shown in Table 6 as plasticizers were added and mixed using a Henschel mixer as in Example 1.

After cooling, the obtained blend was pressed at 175 ° C. for 3 minutes to prepare a sheet having a thickness of about 0.5 mm. Of these, the sheet of Comparative Example 17 had a large amount of initial coloration and had a non-uniform thickness, and therefore the subsequent evaluation was not performed. Other than this comparative example 17,
A sample was prepared from the sheet, placed in a hot air dryer adjusted to 150 ° C., and the degree of discoloration was evaluated by measuring the L ^* , a ^* , and b ^* values with the naked eye and a colorimeter as in Example 1. The results are shown in Table 6.

[0043]

[Table 6] (Footnote) The addition amount in the prescription column is parts by weight.

Compared to Comparative Example 16, Examples 7 and 8 are
The degree of decrease in L ^* value and the degree of discoloration with the naked eye are small. This indicates that potassium citrate has an excellent thermal stability effect.

[0045]

EFFECTS OF THE INVENTION According to the present invention, it is possible to provide a vinylidene chloride copolymer composition which is less affected by heat during molding and has excellent moldability. The vinylidene chloride-based copolymer of the present invention can be used as a raw material for various molded products, but since it has no food hygiene problems, it can be particularly preferably used as a food packaging material.

Claims (1)

[Claims] 1. A vinylidene chloride-based copolymer 100 (A)
Parts by weight, (B) epoxy stabilizer 0.05 to 4 parts by weight,
(C) 0.01 to 3 parts by weight of at least one alkali metal citrate selected from the group consisting of sodium citrate and potassium citrate, and (D) plasticizer 0.1 to 1
A vinylidene chloride-based copolymer composition comprising 0 parts by weight.