JPH1060191A - Linear low-density polyethylene resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition desirable for giving stretch films packaging perishables having excellent antifogging properties by adding a specified polyglycerol fatty acid ester to a linear low-density polyethylene resin. SOLUTION: This composition is prepared by adding 0.2-5 pts.wt. polyglycerol fatty acid ester which, when analyzed by column chromatography, gives a chromatogram in which the peak area of a polyglycerol monofatty acid ester represented by the formula and detected with an ultraviolet absorption detector is at least 70% of the entire area to 100 pts.wt. linear low-density polyethylene resin. In the formula, R is a 6-12C alkyl, an alkenyl or a hydroxyl-substituted alkyl; and n is the average number of the units in the brackets and has a value of 4 or greater. This composition can give films excellent in pressure-sensitive self-adhesiveness, slipperiness, elongation characteristics, antifogging properties, resistance to break by a sharp corner, etc., and free from surface sliminess.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear low-density polyethylene resin composition, and more particularly, to a linear low-density polyethylene having excellent antifogging properties and suitable for forming a stretch film for packaging fresh food products. It relates to a resin composition.

[0002]

2. Description of the Related Art The demand for stretch films for packaging fresh foods such as meat, fish and shellfish, vegetables, fruits and the like is increasing year by year. This type of film is mainly made of plasticized polyvinyl chloride having excellent transparency and self-adhesiveness, and a long-chain fatty acid ester of polyhydric alcohol such as sorbitan or polyglycerin is added as an antifogging agent. As a result, contamination by plasticizer transfer to packaged materials, safety and health issues such as generation of harmful hydrogen chloride gas during film forming, fusing during packaging, or waste incineration have been pointed out. From the viewpoint of environmental protection, the development of a film that can replace plasticized polyvinyl chloride is required.

Along with this, the development of films using ethylene resins such as polyethylene and ethylene-vinyl acetate copolymer and polybutadiene resins has been actively conducted. For example, stretch films based on linear low density polyethylene resins have been developed. The film is disclosed in Japanese Patent Publication No. 3-28460.

[0004]

However, the films obtained from the polyethylene resins and polybutadiene resins disclosed in the above-mentioned publications have no problems in terms of safety and health and pollution, but they are not sufficiently satisfactory as stretch films. . In addition, as a problem of the resin itself, the resin is hard and difficult to elongate and is easily torn, and the self-adhesiveness is insufficient and the slipperiness is insufficient.

On the other hand, stretch films for packaging foodstuffs are required to have excellent antifogging properties, and fatty acid esters of polyhydric alcohols such as sorbitan, glycerin and diglycerin are added as antifogging agents. However, in order to impart sufficient anti-fogging properties to the film using these anti-fogging agents, the amount of the anti-fogging agent added increases so that the film surface becomes slimy, or the film becomes less sticky or slippery. There was a problem of adverse effects.

Japanese Patent Application Laid-Open No. 5-222252 discloses the use of a specific polyethylene resin and polyglycerin fatty acid ester which is also approved as a food additive as an antifogging agent. However, simply using a polyglycerol fatty acid ester as the non-electrolyte surfactant does not provide sufficient anti-fogging properties. Polyglycerin fatty acid ester is
It is produced by the esterification reaction of polyglycerin and fatty acids, but when it is actually esterified, the individual molecules have a distribution of esterification rates, and molecules with high and low esterification rates, and in some cases, are not esterified In many cases, molecules are mixed, and not only fatty acid monoesters but also unreacted polyglycerols, diesters, triesters, tetraesters, and other multi-substituted esterified compounds are mixed. This is because a sufficient antifogging property may not be imparted due to the influence of an object.

Therefore, a resin composition which is suitable for forming a stretch film for packaging foodstuffs and which satisfies anti-fogging properties in addition to self-adhesiveness, slipperiness, moderate elongation properties, resistance to sharp corners, etc. Things are desired.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a polyglycerol fatty acid ester having a high content of polyglycerin monofatty acid ester synthesized from fatty acid and glycidol can be used for food packaging. The present inventors have found that a resin composition suitable for forming a stretch film can be obtained, and have completed the present invention.

That is, the present invention provides a polyglycerol represented by the following general formula (1), which is eluted by column chromatography with respect to 100 parts by weight of a linear low-density polyethylene resin and detected by an ultraviolet absorption detector. It is intended to provide a linear low-density polyethylene resin composition characterized by adding 0.2 to 5 parts by weight of a polyglycerin fatty acid ester having a monofatty acid ester having a peak area of 70% or more of the whole area. Further, the linear low-density polyethylene resin composition is characterized in that the column chromatography is high-performance liquid chromatography using an octadecylsilyl group-bonded silica gel column using an alcohol solvent and / or distilled water as an eluent. To provide. The polyglycerol monofatty acid ester is represented by the following general formula (2)
Wherein the fatty acid and glycidol shown in the above are reacted in the presence of a phosphoric acid-based catalyst to provide the linear low-density polyethylene resin composition. Further, the present invention provides the above linear low-density polyethylene resin composition, wherein the phosphoric acid-based acidic catalyst is phosphoric acid or an acidic phosphoric acid ester. Hereinafter, the present invention will be described in detail.

[0010]

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[0011]

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[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The linear low density polyethylene resin of the present invention has a density of less than 0.94,
It preferably belongs to a region called ultra-low density of less than 0.920. This is because a linear low-density polyethylene having a density of 0.920 or more may lack self-adhesiveness as a stretch film or resistance to sharp corners.

As a method for polymerizing a linear low-density polyethylene, a solution method in which polymerization is generally performed at a temperature equal to or higher than the melting point of a resin,
Generally, there is a gas phase method in which polymerization is performed at a temperature lower than the melting point of the resin. The linear low-density polyethylene used in the present invention is not limited, but is preferably one polymerized by a solution polymerization method. In the gas phase method, a polymer with a wide molecular weight distribution containing low-molecular-weight polyethylene is obtained, whereas when polymerized by the solution polymerization method, the low-molecular-weight polyethylene is dissolved in a solvent and contains low-molecular-weight substances because it is separated from the produced polymer. This is because no polyethylene resin is obtained. If the linear low-density polyethylene resin contains a large amount of low-molecular-weight substances, the added anti-fog agent tends to bleed, causing slimming, reducing the self-adhesiveness of the resin, and decreasing the sliding properties. Not preferred. Such a polymer does not contain a low molecular weight material when polymerized by the solution polymerization method, so that such a phenomenon does not occur. Characteristics do not change.

The linear low-density polyethylene resin can be produced by a conventional method except that it is polymerized by a solution polymerization method. For example, butene-1, hexene-1, octene-1, 4-methylpentene- At least one α-olefin selected from 1 and the like can be copolymerized.

The polyglycerol fatty acid ester to be added to the linear low-density polyethylene resin of the present invention contains at least 70% of the polyglycerin monofatty acid ester represented by the above general formula (1) by measuring the area ratio by HPLC. And can be produced by an addition polymerization reaction of glycidol and a fatty acid. As fatty acids, carbon number 6 ~
As long as it is 22 fatty acids, it may be a saturated fatty acid or an unsaturated fatty acid, a linear fatty acid, a fatty acid having a side chain, or a hydroxyl-substituted fatty acid. In particular,
Caproic acid, caprylic acid, 2-ethylhexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid,
Examples thereof include isostearic acid, oleic acid, linoleic acid, behenic acid, erucic acid, ricinoleic acid, and hydroxystearic acid. These can be used alone or in combination of two or more.

The reaction between the fatty acid and glycidol is preferably carried out in the presence of an acidic catalyst. Examples of the acidic catalyst include phosphoric acids and esters of phosphoric acid. Specific examples thereof include phosphoric acid, phosphoric anhydride, polyphosphoric acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, and tetraphosphoric acid. Acids or acid phosphates such as methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, 2-ethylhexyl acid phosphate, and the like can be used. In addition, as these acidic phosphates, any of a monoester body, a diester body, and a mixture thereof can be used. Further, one kind of the above-mentioned acidic catalyst may be used alone, or two or more kinds may be used in combination.

The amount of the catalyst added is 0.01 to
It is preferably 10% by weight, more preferably 0.1 to 5% by weight. If the amount is less than 0.01% by weight, the reaction rate is low. On the other hand, if the amount exceeds 10% by weight, the effect cannot be expected to be improved. This is because a large number may be generated.

The addition polymerization reaction is carried out by taking a fatty acid in a reaction vessel, adding the above-described catalyst thereto, and adding glycidol little by little. The reaction temperature is 50 to 180 ° C, preferably 70 to 160 ° C, more preferably 120 to 140 ° C.
° C. If the temperature is lower than 50 ° C., the reaction rate is low.
If the temperature exceeds 0 ° C., coloring becomes severe. Particularly, at 230 ° C. or higher, glycidol is decomposed to cause a side reaction, which is not preferable. A low-boiling compound that does not react with glycidol may be added to the addition polymerization reaction in order to prevent an increase in the reaction temperature. The reaction is desirably performed in a nitrogen gas atmosphere, and may be pressurized if necessary.

Water is added to the obtained reaction solution containing the polyglycerin fatty acid ester, followed by heating and dehydration, whereby unreacted glycidol contained in the reaction solution and oxirane group-containing compounds considered as by-products are removed. The derived oxirane group concentration can be reduced. The amount of water to be added is preferably selected in the range of 0.1 to 20% by weight, particularly preferably in the range of 1 to 10% by weight, based on the polyglycerin fatty acid ester contained. If the amount of water is less than 0.1% by weight, unreacted glycidol cannot be sufficiently reduced, while if it exceeds 20% by weight, the post-treatment operation becomes complicated, which is not preferable. Unreacted glycidol can be converted to glycerin by heating. The heating temperature is preferably in the range of 60 to 200 ° C, particularly preferably in the range of 80 to 160 ° C. If the heating temperature is lower than 60 ° C., the concentration of unreacted glycidol and remaining oxirane groups cannot be sufficiently reduced, while if it exceeds 200 ° C., the product polyglycerin fatty acid ester is colored. The heating time is 0.5 to 15 hours, particularly preferably 1 to 7 hours, depending on the temperature. Dehydration can be performed by distillation, azeotropic distillation, vacuum distillation, or the like. The heating temperature during the distillation is preferably selected in the range of 100 to 200 ° C, particularly preferably in the range of 110 to 160 ° C. If the heating temperature is lower than 100 ° C., it is not sufficient to remove water contained in the polyglycerin fatty acid ester of the product, while if it exceeds 200 ° C., the product polyglycerin fatty acid ester is undesirably colored. . The time for dehydration depends on the temperature and the degree of pressure reduction, but is preferably in the range of 1 to 10 hours, and particularly preferably in the range of 1 to 6 hours. When a solvent is used, it can be removed by this dehydration operation, but may be removed by another operation.

The content of the monofatty acid ester in the obtained polyglycerin fatty acid ester is measured according to the following analysis conditions. Reversed-phase partition column analysis using silica gel bonded with octadecylsilyl group (ODS group), octylsilyl group, butylsilyl group, trimethylsilyl group, and phenylsilyl group as a carrier, silica gel having aminopropyl group and cyanopropyl group as a carrier A normal phase distribution column analysis method includes an ion exchange column analysis method using silica gel having a quaternary ammonium group and a phenylsulfonic acid group as a carrier, and an adsorption column analysis method using porous silica gel as a carrier. Among these, ODS
The method is preferably a reversed-phase distribution column analysis method using silica gel having a group bonded as a carrier. Further, the column size is preferably 4.6 mmφ × 250 mm or more in order to improve the separation ability, and it is more preferable to connect the columns in series because the separation ability can be improved.

The case of analysis by the reversed-phase distribution column analysis method will be described below. Since the developing solvent varies depending on the type of the fatty acid of the polyglycerin fatty acid ester and the number of moles of glycidol added, it is preferable to determine the developing solvent from the solubility and separation properties of the test sample. Specifically, as a specific developing solvent having excellent solubility and separability of an analyte, an alcohol-based solvent and / or distilled water is preferable. Specifically, methanol is used for polyglycerol laurate. It is preferable to use ethanol for the polyglycerol stearate.

The flow rate of the developing solvent is selected according to the pressure resistance of the column used and the degree of separation of the obtained chromatogram.
Usually, it is in the range of 0.05 to 1.0 ml / min, more preferably in the range of 0.1 to 0.8 ml / min. The column temperature is preferably in the range 30-60 ° C. The wavelength of the ultraviolet absorption detector is 210 nm.

For a sample to be subjected to HPLC, it is preferable to use a developing solution to be used as a solvent, and a concentration and an injection amount are selected so as to be excellent in solubility and separation of an analyte. Specifically, the sample concentration is preferably 1 to 50%, and the injection volume is preferably 0.1 to 20 μl.

The measurement of the content is as follows. In HPLC analysis using an ODS column, elution is generally performed in the order of polarity. Therefore, in the case of polyglycerins, unsubstituted polyglycerol having high polarity is eluted first, and then polyglycerin monofatty acid ester and polyglycerin difatty acid ester are detected. On the other hand, in the case of glycerin monofatty acid esters, polyglycerin monoester having high polarity is eluted first, and glycerin monoester is eluted last. Therefore, the standard products of polyglycerin and glycerin monofatty acid were analyzed by HPLC under the same conditions, the retention times of the standard products and the samples were compared and examined, and those eluted after the glycerin monoester was eluted were replaced with polyesters of diester or higher. And The content (%) of the polyglycerol monofatty acid ester was represented by the peak area ratio according to the following. From the analysis chart, the peak area of polyglycerin, the peak area of polyglycerin monofatty acid ester (referred to as “polyglycerin, but in the present invention, the glycerin portion includes from polyglycerin to monoglycerin), and the peak area of diester or more. The peak area of the substituted ester component was determined. Then, it was calculated according to the following equation.
In addition, the solvent whose peak position did not overlap with any of the peaks of polyglycerin, monofatty acid ester, and polysubstituted ester of diester or higher was selected. The following formula assumes that the retention time of the solvent is after the elution of the diester.

[0025]

Formula: Content (%) of polyglycerin monofatty acid ester = ｛peak area of polyglycerin monofatty acid ester / (peak area of polyglycerin + peak area of polyglycerin monofatty acid ester + polyester of diester or more) Peak area) x 100 (%)

0.2 to 5 parts by weight of a polyglycerin monofatty acid ester compound having a high content of polyglycerin monofatty acid ester is added to 100 parts by weight of the linear low-density polyethylene resin as an antifogging agent. 4 to 3
It is preferable to add parts by weight. When the amount of the antifogging agent is 0.
If the amount is less than 2 parts by weight, a sufficient anti-fogging effect is not exhibited. If the amount exceeds 5 parts by weight, the amount of bleeding becomes too large, resulting in film slimming and reduced slipperiness, which is not preferable, and is too large as required. Is also uneconomical.

The linear low-density polyethylene resin composition of the present invention may further contain a tackifier, a wax such as a fatty acid amide, an antioxidant, a stabilizer, and the like, if necessary.

The linear low-density polyethylene resin composition of the present invention can be produced by adding an antifogging agent to the linear low-density polyethylene resin by a usual method. For example, a linear ultra-low density polyethylene resin obtained by a polymerization reaction and an anti-fog agent may be kneaded using a twin-screw extruder.
It can be formed into a film by a die-extruder or the like.

[0029]

The present invention will be further described with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.

(Test Method) (1) Antifogging property 150 ml of water at 20 ° C. was put into a 300 ml wide-mouthed bottle.
Seal the mouth with film and place the bottle in a refrigerator at 5 ° C.
After 0 minutes, the bottle was taken out and the inner surface of the film was examined for fogging. The evaluation was made in five steps according to the following criteria. 5: Completely transparent and free from cloudiness 4: Almost transparent but slightly water droplets 3: Large water droplets adhere but quite transparent 2: Large water droplets adhere and opaque throughout 1: Fine water droplets adhere to the entire surface and are opaque. (2) Suitability for packaging Cucumbers were placed in a tray made of expanded styrene, packaged by hand, and evaluated according to the following criteria. ：: no wrinkles are observed on the film surface, △: small wrinkles are observed at the portion where the film contacts the tray,
×: Wrinkles were observed or the film was torn on the film surface. (3) Surface Properties The surface state of the formed film was visually observed or touched with the hand to evaluate the degree of slimming and whitening according to the following criteria. ：: no slimming or whitening is observed at all; △: slimming or whitening is slightly observed ×: slimming or whitening is remarkably observed

Synthesis Example 1 0.5 mol (100.1 mol) of lauric acid was placed in a 1-liter four-necked flask equipped with a nitrogen inlet tube, a stirrer, a cooling tube, a temperature controller, and a dropping cylinder.
6g) and 0.0622g of phosphoric acid (85% product)
Heated to 40 ° C. Then, while maintaining the reaction temperature at 140 ° C., 3.0 mol (222.24 g) of glycidol was added dropwise over 5 hours. The temperature was further maintained, and the reaction was continued for 26 hours. Then, continue to add 2% by weight of water to the same flask.
After the addition, the temperature inside the flask was heated to 140 ° C. with stirring, and the temperature was maintained at this temperature under reflux for 2 hours. Next, the temperature inside the flask was raised to 140 ° C., and while maintaining this temperature, the inside of the flask was depressurized and dehydrated by vacuum distillation. 4 vacuum distillations
The final degree of decompression after 10 hours was 10 mmHg.
When the obtained polyglycerin fatty acid ester (hexaglycerin monolaurate) was evaluated using the following HPLC analysis conditions, the monoester content was 8%.
7.7%.

(Analysis conditions of HPLC) Column: Wakosil II 5C18HG (manufactured by Wako Pure Chemical Industries, Ltd .: column having an octadecylsilyl group as a functional group which is a reversed-phase distribution column, size: 4.6 mm)
φ × 250 mm), developing solvent: methanol, flow rate: 0.
2 ml / min. , Column oven temperature: 40 ° C., detection method: ultraviolet absorption method (λ = 210 nm), sample concentration: 5
% (Solvent: methanol), injection volume: 10 μl, retention time of each component: polyglycerin: before 14 minutes, monoester: from 14 minutes to 16.5 minutes, diester and above: from 16.5 minutes, methanol component : 18 minutes.

Synthesis Example 2 4.0 mol of glycidol
(296.32 g) Except for using, the same operation as in Synthesis Example 1 was performed. After cooling, the reaction product was taken out to obtain about 400 g of octaglycerin monolaurate. The obtained polyglycerol monolaurate (octaglycerol monolaurate) was converted to H
When evaluated by PLC, the content of monoester was 8
It was 4.5%.

Synthesis Example 3 5.0 mol of glycidol
(370.40 g) Except for using, the same operation as in Synthesis Example 1 was performed. After cooling, the reaction product was taken out to obtain about 470 g of decaglycerin monolaurate. The obtained polyglycerol monolaurate (decaglycerin monolaurate) was converted to HPL in the same manner as in Synthesis Example 1.
When evaluated in C, the monoester content was 77.2.
%Met.

Reference Example 1: Reaction of fatty acid with polyglycerin Polyglycerin (Daicel Chemical Industries, Ltd.) was placed in a 1-liter four-necked flask equipped with a nitrogen inlet tube, a stirrer, a cooling tube, a temperature controller, and a dropping cylinder. PGL manufactured by
06: hexaglycerin, hydroxyl value 960) 175.3
g (0.5 mol) and heated to 80 ° C., while maintaining the reaction temperature at 80 ° C., 0.5 mol (10 mol) of lauric acid.
0.16 g) was added and dissolved. Next, 0.75 g of sodium carbonate and 0.25 g of sodium bisulfite were added, and an esterification reaction was performed at 210 ° C. After 2 hours of reaction, the acid value became 0.89 mgKOH / g. After cooling to 100 ° C., the reaction product was taken out. The obtained polyglycerol monolaurate was converted to H in the same manner as in Synthesis Example 1.
When evaluated by PLC, the monoester content was 5%.
It was 5.1%.

Reference Examples 2 and 3: Evaluation Results of Commercially Available Polyglycerol Fatty Acid Esters As commercial polyglycerin fatty acid esters produced from the reaction of polyglycerin and fatty acids, two products of SY Glyster (manufactured by Sakamoto Yakuhin Kogyo) ML-500, ML-750). When these polyglycerin monolaurates were evaluated by HPLC in the same manner as in Synthesis Example 1, ML-500, M
The content of the monoester of L-750 was 52.0
%, 44.3%. These are referred to as Reference Examples 2 and 3, respectively.

(Examples 1 to 5, Comparative Examples 1 to 5) A linear low-density polyethylene resin having a density of 0.910 obtained by a solution polymerization method (Ultzex 10 manufactured by Mitsui Petrochemical Industries, Ltd.)
20L) 100 parts by weight of the antifogging agent shown in Table 1 was added in the amount shown in Table 2. This was kneaded using a twin screw extruder to produce an extruded pellet. Furthermore, at a die temperature of 200 ° C., a thickness of 20
A μm film was formed. The obtained film was evaluated for antifogging property, packaging suitability and surface condition. Table-Results
It is shown in FIG.

(Examples 6 to 8, Comparative Examples 6 to 8) A linear low-density polyethylene resin having a density of 0.905 (ethylene-butene-1 copolymer, butene-1 content) obtained by a solution polymerization method: 14% by weight, weight average molecular weight / number average molecular weight = 3.
5) 100 parts by weight of the antifogging agent shown in Table 1 was added to Table 3
Was added in the amount indicated. This was kneaded using a twin screw extruder to produce an extruded pellet. Further, a film having a thickness of 20 μm was formed by a T-die method at a die temperature of 200 ° C. The obtained film was evaluated for antifogging property, packaging suitability and surface condition. The results are shown in Table-3.

(Examples 9 to 10 and Comparative Examples 9 to 10) Linear low-density polyethylene having a density of 0.930 obtained by solution polymerization (Ultzex 301 manufactured by Mitsui Petrochemical Industries, Ltd.)
0F), the antifogging agents shown in Table 1 were added in the amounts shown in Table 4, and films were formed in the same manner as in Example 1.
Further, a linear low-density polyethylene having a density of 0.910 obtained by a gas phase method (manufactured by CDF: NOR SOFLEX FW19)
00) and the antifogging agents shown in Table 1 were added in the amounts shown in Table 4, and a film was formed in the same manner as in Example 1.
The antifogging property, packaging suitability and surface state of the obtained film were evaluated. Table 4 shows the evaluation results.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

Industrial Applicability The linear low-density polyethylene resin composition of the present invention is suitable for forming a stretch film for packaging fresh foods, and the film has self-adhesiveness, slipperiness, elongation properties, antifogging properties, Excellent resistance to sharp corners, etc., and no slimming occurs on the film surface.

Claims (4)

[Claims] 1. A polyglycerol monofatty acid ester represented by the following general formula (1), which is eluted by column chromatography with respect to 100 parts by weight of a linear low-density polyethylene resin and detected using an ultraviolet absorption detector. A linear low-density polyethylene resin composition comprising 0.2 to 5 parts by weight of a polyglycerin fatty acid ester having a peak area of 70% or more of the total area. Embedded image 2. The linear chromatography according to claim 1, wherein the column chromatography is a high performance liquid chromatography using an octadecylsilyl group-bonded silica gel column using an alcohol solvent and / or distilled water as an eluent. Low density polyethylene resin composition. 3. A polyglycerol monofatty acid ester,
3. The linear low-density polyethylene resin composition according to claim 1, wherein the fatty acid represented by the following general formula (2) is reacted with glycidol in the presence of a phosphoric acid-based catalyst. Stuff. Embedded image 4. The linear low-density polyethylene resin composition according to claim 3, wherein the phosphoric acid-based acidic catalyst is phosphoric acid or an acidic phosphoric acid ester.