JPH07292194A - Resin composition - Google Patents

Abstract

PURPOSE:To obtain a resin composition comprising a vinyl chloride-based polymer, having transparency suitable as a food packaging material and causing no initial discoloration thereof. CONSTITUTION:This resin composition which comprises a vinyl chloride-based polymer is obtained by an aqueous suspension polymerization of a vinyl chloride- based monomer in the presence of a hydrotalcite of the formula M<2+>1-xM<3+>x(OH)2A<n->x/n.mH2O (M<2+> is a divalent metal ion; M<3+> is a trivalent metal ion; A<n-> is a n-valent anion such as CO3<2-> or SO4<2-> ; 0<x<0.5; n is a Positive number of 1-4; m is 0 or a positive number of <=0.3) coated with an organic compound selected from higher fatty acids, higher fatty acid salts, organic sulfonic acid metal salts, higher fatty acid amides, higher fatty acid esters and waxes.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent transparency,
In addition, the present invention relates to a resin composition which is composed of a vinyl chloride polymer in which color deterioration is suppressed and which is particularly suitable for food packaging.

[0002]

2. Description of the Related Art Conventionally, it has been known to add hydrotalcite when a vinyl chloride polymer is produced by suspension-polymerizing a vinyl chloride monomer. For example, JP-A-61
-207, a suspension stabilizer, and Japanese Patent Laid-Open No. 5-207
No. 170806 discloses a technique for producing a vinyl chloride resin in which hydrotalcite is added as a zinc elution inhibitor or the like.

Further, as an example in which hydrotalcite is added to a vinyl chloride resin composition for food packaging, JP-A-3-41142 discloses a specific amount of a hydrotalcite compound for improving transparency and the like. A resin composition containing a polyvinyl chloride resin in combination with other components is shown, and as the hydrotalcite compound, higher fatty acids such as stearic acid, higher fatty acid metal salts such as alkali metal oleate, and dodecyl are used for the surface. It is described that organic sulfonic acid metal salts such as alkali metal salts of benzene sulfonic acid, higher fatty acid amides, higher fatty acid esters or wax coated with wax can also be used. JP-A-4-359946 discloses that a synthetic hydrotalcite compound having a water of crystallization of 0.3 or less is added to a chlorine-containing resin together with other components to cause color deterioration during extrusion molding at high temperature and eye stains and plate-out. There has been proposed a resin composition for food packaging which has improved transparency while preventing the occurrence of such problems.

[0004]

By the way, the water of crystallization of hydrotalcite is desorbed from the crystal by firing at 185 to 230 ° C. or higher, but the hydrotalcite thus fired does not come into contact with water. It is known that the water of crystallization is easily re-incorporated into the crystal upon moisture absorption. Therefore, it is considered impossible to improve the transparency and color deterioration even if the hydrotalcite-calcined product is added in the suspension polymerization process of vinyl chloride monomer using water as a medium. All of the conventional vinyl chloride-based resin compositions intended for the purpose are produced by adding hydrotalcite to a polyvinyl chloride resin. However, if hydrotalcite can be added stably at the stage of aqueous suspension polymerization of vinyl chloride monomer, it is extremely useful as a method for industrially obtaining a resin composition suitable for food packaging having excellent transparency. It is a highly technical technology.

The inventors of the present invention have made extensive studies paying attention to the above-mentioned points. As a result, specific hydrotalcite particles are surface-coated with an organic substance containing a higher fatty acid, and in the presence of this hydrotalcite. It was confirmed that a vinyl chloride polymer obtained by subjecting a vinyl chloride monomer to aqueous suspension polymerization has transparency which is particularly suitable for food packaging.

The present invention has been completed based on the above findings, and an object thereof is to provide a vinyl chloride resin composition having transparency suitable for food packaging materials and having little initial coloring.

[0007]

The resin composition according to the present invention for achieving the above object is represented by the following general formula (1), and the particle surface has higher fatty acids, higher fatty acid metal salts, organic Obtained by aqueous suspension polymerization of vinyl chloride-based monomers in the presence of hydrotalcite coated with an organic material selected from sulfonic acid metal salts, higher fatty acid amides, higher fatty acid esters and waxes. It is characterized in that it is composed of a vinyl chloride polymer. M ²⁺ _1-X M ³⁺ _X (OH) ₂ A ^n- _{X / n} · mH ₂ O (1) In the formula (1), M ²⁺ is a divalent metal ion and M ³⁺ is 3 Valent metal ion, A ^n- is n such as CO ₃ ^2- or SO ₄ ^2-
Valent anion, x is 0 <x <0.5, n is a positive number of 1 to 4, m is 0 or a positive number of 0.3 or less.

The hydrotalcite used in the present invention is represented by the above general formula (1). The divalent metal of M ²⁺ is Mg or / and Zn, and the trivalent metal of M ^3+. However, the composition of Al is general. However, it is important that the water of crystallization m is in the range of 0 or 0.3 or less, and when m exceeds 0.3, the transparency of the resin composition obtained is impaired, and the initial coloration remarkably appears. become. Hydrotalcite is preferably a fine powder having an average particle size in the range of 0.01 to 1 μm. Within this range, the smaller the average particle size, the less light scattering is likely, which is advantageous for imparting transparency. Becomes

The hydrotalcite particles having the composition of the general formula (1) are previously selected from higher fatty acids, higher fatty acid metal salts, organic sulfonic acid metal salts, higher fatty acid amides, higher fatty acid esters and waxes on the surface. The organic matter is coated. Examples of higher fatty acids include stearic acid, examples of higher fatty acid metal salts include oleic acid alkali metal salts, and examples of organic sulfonic acid metal salts include dodecylbenzenesulfonic acid alkali metal salt.
Each is preferably used. The surface treatment amount of hydrotalcite is in the range of 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of hydrotalcite. Such hydrotalcite powder having a crystal water m of 0 to 0.3 and being surface-treated with an organic substance is, for example, "Alkamizer 2" and "Alkamizer 4-2" manufactured by Kyowa Chemical Industry Co., Ltd. , "Alcamizer 7-2",
There are commercially available products such as "DHT4A-2", and these can also be used.

The above-mentioned hydrotalcite is added to a polymerization system in which a vinyl chloride monomer is subjected to aqueous suspension polymerization. The vinyl chloride-based monomer to be polymerized is a vinyl chloride monomer alone or a monomer mixture containing the monomer as a main component. Examples of the monomer that can be used in combination with the vinyl chloride monomer include vinylidene chloride and other halogenated vinyl monomers, butyl acrylate, ethyl acrylate, methyl acrylate and other acrylic esters, methyl methacrylate, glycidyl methacrylate and other methacrylic acid monomers. Examples thereof include acid esters, vinyl carboxylates such as vinyl acetate, and alkyl vinyl ethers such as cetyl vinyl ether and isobutyl vinyl ether, and these are blended in the range of 30% by weight or less based on the total amount of all monomers.

The preferred timing of adding hydrotalcite to the polymerization system is to add it before the polymerization conversion rate reaches 20%, particularly preferably before the initiation of polymerization.
The amount added is 10 to 1000 ppm, preferably 20 to 500 ppm, based on the charged weight of the vinyl chloride monomer.
More preferably, it is set in the range of 40 to 500 ppm. 1
The use of hydrotalcite in excess of 000 ppm causes the transparency of the obtained vinyl chloride polymer composition to be impaired, while the initial coloration of the obtained vinyl chloride polymer composition is manifested in less than 10 ppm.

Aqueous suspension polymerization is carried out by a conventional method. The polymerization conditions are usually such that the ratio of the vinyl chloride monomer to the aqueous medium is 80 to 300 parts by weight of water to 100 parts by weight of the monomer, and the polymerization temperature is suitably 35 to 70 ° C. A suspension stabilizer, a polymerization initiator and the like are added during the polymerization.

Preferred suspension stabilizers include polyvinyl alcohol, partially saponified polyvinyl alcohol, methyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, which may be used alone or in combination of two or more. The preferred amount of the suspension stabilizer used is 300 to 5000 ppm, preferably 40, based on the weight of the vinyl chloride monomer charged.
0-3500ppm, more preferably 500-2000pp
It is in the range of m. If the amount of suspension stabilizer used is less than 300 ppm, the polymerization tends to be unstable, and if it exceeds 5000 ppm, the resulting polymer particles become too fine.

As the polymerization initiator, diisopropyl peroxydicarbonate, di (ethoxyethyl) peroxydicarbonate, dicyclohexyl peroxydicarbonate, t-butyl peroxyneodecanate, cumylperoxyneodecanate and t-butyl are used. Peroxypivalate or the like can be used.

The vinyl chloride polymer obtained by suspension polymerization preferably has an average particle size in the range of 100 to 150 μm as a property, and has a degree of polymerization of 700 to 1,
It is preferably 500.

When the resin composition comprising the vinyl chloride polymer according to the present invention is used as a food packaging material, it is formed as follows. First, in addition to a non-toxic calcium-zinc-based heat stabilizer, a vinyl chloride polymer, a plasticizer consisting of an ester of an aliphatic alcohol having 6 to 10 carbon atoms and adipic acid, and a relatively large amount of epoxidation An antifog agent such as soybean oil and a nonionic surfactant, for example, a lubricant such as a higher fatty acid wax is added to prepare a blended composition. As other stabilizing aids and addition aids, for example, β-diketone compounds such as stearoylbenzoylmethane and palmitoylbenzoylmethane can be added. The preferred blending ratio of these components is 0.05 to 100 parts by weight of the vinyl chloride polymer, and the heat stabilizer is 0.05 to 100 parts by weight.
5 parts by weight, the plasticizer is used in an amount of 20 to 80 parts by weight, and the other additives are used in an appropriate amount ratio for the purpose of further improving thermal stability, processability or transparency.

Then, these compounded compositions are used at a temperature of about 100 to 150 ° C. for 5 to 5 times using a high speed mixer equipped with a heating jacket such as a Henschel mixer.
A resin composition is obtained by an operation of mixing for 40 minutes, and finally a molding means such as an extrusion molding method or a calender molding method is applied to form a desired food packaging material.

[0018]

^Operation : General formula applied in the present invention: M 2 ⁺ _1-X M ³⁺ _X (O
H) ₂ A ⁿ⁻ _{X / n} · mH ₂ O (wherein M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, and A ⁿ⁻ is CO ₃ ²⁻ or SO ₄ ^2−. N-valent anions such as x, 0 <x <0.5,
n is a positive number of 1 to 4, m is 0 or a positive number of 0.3 or less), and the surface of the particle is higher fatty acid, higher fatty acid metal salt, organic sulfonic acid metal salt, higher fatty acid amide,
Hydrotalcite coated with an organic substance selected from higher fatty acid esters and wax is extremely stable in water, and even if it is added in the process of aqueous suspension polymerization of vinyl chloride-based monomer, water of crystallization remains. The phenomenon of being re-adsorbed and impairing transparency or causing initial coloring is effectively suppressed. This stabilizing effect, combined with the original transparency-imparting function of hydrotalcite, provides excellent transparency and coloring by adding vinyl chloride-based monomer to the aqueous suspension polymerization system, which was previously considered impossible. It is possible to obtain a resin composition without deterioration.

Therefore, according to the present invention, it is possible to provide a resin composition which is made of a vinyl chloride polymer and which is suitable for food packaging and has excellent transparency and no initial coloration.

[0020]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. The resin composition is evaluated as a food packaging material, but the use of the present invention is not limited to this.

Example 1 (1) Preparation of vinyl chloride polymer: 2700 g of deionized water, 1.0 g of synthetic hydrotalcite (500 ppm with respect to vinyl chloride monomer) were placed in an autoclave having an internal volume of 5 liters,
Polyvinyl alcohol having a saponification degree of 78 to 82 mol% and a viscosity of a 4% aqueous solution at 20 ° C. of 37 to 45 cps.
4 g, 20% of a 4% aqueous solution with a saponification degree of 76-80 mol%
1.4 g of polyvinyl alcohol having a viscosity of 11 to 15 cps at 0 ° C., 0.2 cumyl peroxyneodecanoate
g, and 0.5 g of di (2-ethoxyethyl) peroxydicarbonate was charged.

The synthetic hydrotalcite has a composition represented by the following chemical formula (2), and the average particle diameter is obtained by coating the surface of particles with stearic acid in an amount of 2 parts by weight per 100 parts by weight of hydrotalcite. A fine powder of 0.6 μm was used. _{Mg 0.69 Al 0.31 (OH) 2} (CO 3) 0.155 0.1H 2 O ... (2)

After removing air in the autoclave with a vacuum pump, 2000 g of vinyl chloride monomer was inserted and polymerization was started at 57 ° C. with stirring. Eight hours after the start of the polymerization, the internal pressure of the autoclave decreased by ² kg / cm ² , so the polymerization reaction was stopped. Then, unreacted monomers were discharged, and the polymer slurry was dehydrated and dried to give 1650 g of vinyl chloride polymer.
Got

(2) Evaluation as a food packaging material Using the obtained vinyl chloride polymer (1500 g), a compounding composition shown in Table 1 was prepared. The blended composition was put into a heated Henschel mixer, and sufficiently mixed until a temperature of 110 ° C. was obtained, and dry blending was performed. Mix the mixture with Labo Plastmill [Toyo Seiki Seisakusho, single-screw extruder D20-2
5], extrusion molding was performed under the following conditions. Screw: diameter 20mm, length 500mm Die: T-die (width 150mm, thickness 0.1mm) Temperature: C1 / C2 / C3 / Dies = 170/175/180/19

[0025]

[Table 1]

The molded sheets were evaluated for transparency and initial colorability. As for transparency, a sheet with a thickness of 25 mm is wound around the core, "excellent" when the core is transparent and the core is clearly visible, "good" when the core is slightly hazy, and the core is not hazy The time was judged as "very bad". In addition, the initial colorability was obtained by cutting a test piece from a sheet, stacking 30 pieces on a die, and using a press molding machine.
Press molding at 70 ℃, 100kg / cm ² , 5 minutes,
The degree of initial coloring was determined using the obtained press plate having a thickness of 3 mm. The results are shown in Table 2.

Example 2 The addition amount of synthetic hydrotalcite was changed to 2.0 g (1000 ppm with respect to vinyl chloride monomer), and the others were changed to Example 1
Under the same conditions as above, 1640 g of a vinyl chloride polymer was obtained. The vinyl chloride polymer was evaluated for transparency and initial colorability in the same manner as in Example 1. The results are also shown in Table 2.

Example 3 As a synthetic hydrotalcite, the composition was represented by the following chemical formula (3), and the average of the particles whose surface was coated with stearic acid in an amount of 2 parts by weight per 100 parts by weight of hydrotalcite was used. A fine powder having a particle size of 0.6 μm was used. Mg _0.69 Al _0.31 (OH) ₂ (CO ₃ ) _0.155 0.3H ₂ O (3)

Under the same conditions as in Example 1 except for above, 1640 g of a vinyl chloride polymer was obtained, and the transparency and the initial colorability were evaluated in the same manner as in Example 1. The results are also shown in Table 2.

Example 4 As a synthetic hydrotalcite, the composition represented by the following chemical formula (4) was used, and the average particle size was obtained by coating the surface of particles with stearic acid in an amount of 2 parts by weight per 100 parts by weight of hydrotalcite. A fine powder having a particle size of 0.6 μm was used. Mg _0.50 Zn _0.17 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 0.1H ₂ O ... (4)

Other than the above, 1645 g of a vinyl chloride polymer was prepared under the same conditions as in Example 1, and the transparency and the initial colorability were evaluated in the same manner as in Example 1. The results are also shown in Table 2.

Comparative Example 1 No synthetic hydrotalcite was added.
1630 g of a vinyl chloride polymer was produced under the same conditions as above, and the transparency and the initial colorability were evaluated in the same manner as in Example 1. The results are also shown in Table 2.

Comparative Example 2 As a synthetic hydrotalcite, the composition was represented by the following chemical formula (5), and the surface of the particles was coated with stearic acid in an amount of 2 parts by weight per 100 parts by weight of hydrotalcite. A fine powder having a particle size of 0.6 μm was used. _{Mg 0.69 Al 0.31 (OH) 2} (CO 3) 0.155 0.54H 2 O ... (5)

1635 g of a vinyl chloride polymer was prepared under the same conditions as in Example 1 except for the above, and the transparency and the initial colorability were evaluated in the same manner as in Example 1. The results are also shown in Table 2.

Comparative Example 3 As synthetic hydrotalcite, the composition was represented by the following chemical formula (6), and the average was obtained by coating the surface of particles with stearic acid in an amount of 2 parts by weight per 100 parts by weight of hydrotalcite. A fine powder having a particle size of 0.6 μm was used. Mg _0.50 Zn _0.17 Al _0.33 (OH) ₂ (CO ₃ ) _0.165 0.54 H ₂ O ... (6)

Other than the above, 1630 g of a vinyl chloride polymer was prepared under the same conditions as in Example 1, and the transparency and the initial colorability were evaluated in the same manner as in Example 1. The obtained results are also shown in Table 2.

Comparative Example 4 Comparative Example 2 except that fine powder of hydrotalcite coated with stearic acid and having an average particle size of 0.4 μm was used.
A vinyl chloride polymer was prepared in the same manner as in. The obtained vinyl chloride polymer was evaluated for transparency and initial colorability in the same manner as in Example 1. The results are also shown in Table 2.

Comparative Example 5 A slurry of a polymer obtained by polymerizing without adding hydrotalcite was dehydrated and dried in the same manner as in Comparative Example 1.
Under the same conditions as in Example 1, hydrotalcite coated with stearic acid was added in the same amount as in Example 1. The obtained vinyl chloride polymer was evaluated for transparency and initial colorability in the same manner as in Example 1. The results are also shown in Table 2.

[0039]

[Table 2]

From the results shown in Table 2, all of the vinyl chloride resin compositions of Examples had excellent transparency and no initial coloration was observed, but Example 2 contained a large amount of synthetic hydrotalcite. Therefore, the result shows that transparency is slightly reduced.
On the other hand, Comparative Example 1 in which the synthetic hydrotalcite was not added had good transparency but exhibited initial coloring, and the water of crystallization was m.
In Comparative Examples 2 to 4 in which the ratio exceeds 0.3, the transparency or the initial colorability deteriorates. Comparative Example 5 in which hydrotalcite obtained by coating a vinyl chloride polymer with stearic acid was blended
Then, transparency could not be secured.

[0041]

As described above, according to the present invention, a fine powder of hydrotalcite having a specific composition coated with an organic substance containing a higher fatty acid is added to a polymerization system during the aqueous suspension polymerization process of vinyl chloride monomer. It is possible to provide a resin composition composed of the vinyl chloride polymer obtained as described above and having excellent transparency and no initial coloration. Therefore, it becomes possible to produce a high-quality food packaging material by molding this into a desired shape.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naonori Asada 1 1 Funami-cho, Minato-ku, Nagoya, Aichi Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute

Claims (1)

[Claims] 1. A compound represented by the following general formula (1) and having a particle surface selected from higher fatty acids, higher fatty acid metal salts, organic sulfonic acid metal salts, higher fatty acid amides, higher fatty acid esters and waxes. A resin composition comprising a vinyl chloride polymer obtained by aqueous suspension polymerization of a vinyl chloride monomer in the presence of hydrotalcite coated with an organic substance. M ²⁺ _1-X M ³⁺ _X (OH) ₂ A ^n- _{X / n} · mH ₂ O (1) In the formula (1), M ²⁺ is a divalent metal ion and M ³⁺ is 3 Valent metal ion, A ^n- is n such as CO ₃ ^2- or SO ₄ ^2-
Valent anion, x is 0 <x <0.5, n is a positive number of 1 to 4, and m is 0 or a positive number of 0.3 or less.