JPH0616849A - Anti-fogging plastic film and prevention of fogging of plastic film - Google Patents

Abstract

PURPOSE:To obtain a film resisting to whitening and blocking and having excellent persistent transparency and anti-fogging effect by applying an aqueous composition of a specified acrylamide copolymer to a plastic film and drying the film. CONSTITUTION:A plastic film (e.g. PVC film) is coated with an aqueous composition of an acrylamide copolymer having a weight-average molecular weight of 1000-50000 and comprising linearly and randomly arranged 65-99mol% repeating ethylene units of formula I, 0-15mol% repeating acrylate units of formula II (wherein R<1> is 1-4C alkyl) and 1-35mol% repeating acrylamide units of formula III (wherein R<2> is 2-8C alkylene; R<3> and R<4> are each R<1>; R<5> is 1-12C alkyl, 6-12C aryl, alkyl or a 6-12C alicyclic alkyl; and X is halogen, CH3OSO3 or C2H5OSO3) and dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antifogging plastic film and a method for producing the same. In addition,
The plastic film mentioned here includes not only a film-shaped one but also a sheet-shaped one.

[0002]

2. Description of the Related Art Plastic films of polyethylene, polyvinyl chloride, ethylene-vinyl acetate copolymer, polypropylene, polyester, polyamide and the like are widely used as packaging materials for agricultural houses or foods and sundries. In that case, since these plastic films have a hydrophobic surface, water drops adhere to the inner surface of the film,
In agricultural houses, it blocks sunlight and causes growth inhibition of crops. In food packaging films,
There is a problem that the contents cannot be seen.

In order to solve such problems, a drop-free agent,
A plastic film with anti-fogging property is produced by kneading a surface-active agent called a drip agent or an anti-fog agent into a plastic raw material resin and molding or coating the surface of the molded plastic film. ing.

Examples of the antifogging agent used in such a case include sorbitan lauric acid ester, sorbitan myristic acid ester, sorbitan palmitic acid ester, sorbitan stearic acid ester, sorbitan oleic acid ester and other fatty acid esters of sorbitan, and glycerin. Lauric acid ester, oleic acid ester of glycerin, glycerin fatty acid ester such as polyglycerin stearic acid ester, and polyoxyalkylene alkylphenyl ether are known.

[0005]

However, in the plastic film in which the conventionally known antifogging agent as described above is kneaded or applied, for example, when a stearic acid ester of sorbitan is used, Since the antifogging agent is extremely accumulated on the surface, it causes whitening of the film surface, impairing its appearance, and blocking between films at high temperatures.

When an antifogging agent such as sorbitan oleate is used, the whitening phenomenon does not occur.
The problem of blocking remains an issue.

As another problem, it has been pointed out that the antifogging effect is insufficiently sustained. That is, as an action mechanism of antifogging when these antifogging agents are used, for example, in the case of a kneading type, the antifogging effect appears due to the action of the antifogging agent bleeding on the surface, but the antifogging agent is aged. It is said that the anti-fogging effect lasts for a relatively long period of time, since it bleeds out from inside the film sequentially while flowing out together with water droplets. However, it is self-evident that the antifogging effect is lost when there is no more antifogging agent to be bleeding inside the film, and there is still room for improvement in its sustainability.

Further, in the case of the coating type antifogging agent, since it is not replenished from the inside of the film, its durability is shorter than that of the kneading type, and it is in the present situation that the required level is not satisfied.

[0009]

The present invention has been made by paying attention to such a conventional problem, and the formula:

[Chemical 4] An ethylene structural unit represented by

[Chemical 5] (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), 0 to 15 mol% of an acrylate structural unit represented by the general formula:

[Chemical 6] (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
An aqueous composition of 5 mol% of acrylamide copolymer having a weight average molecular weight of 1,000 to 50,000, which is randomly arranged in a linear fashion, is applied to a plastic film and dried, or the acrylamide copolymer is used. The polymer is 3 to 3 with respect to 100 parts by weight of the raw material resin (hereinafter, simply referred to as “parts”).
The object is achieved by blending 0 parts and then forming a film.

[Requirements Constituting Means] Acrylamide Copolymer The acrylamide copolymer used in the present invention has the formula:

[Chemical 7] An ethylene structural unit represented by

[Chemical 8] (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), 0 to 15 mol% of an acrylate structural unit represented by the general formula:

[Chemical 9] (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
It is an acrylamide-based copolymer having a weight average molecular weight of 1,000 to 50,000, which is composed of 5 mol% and is randomly arranged.

The formula in the acrylamide-based copolymer:

[Chemical 10] The proportion of ethylene structural units represented by is 65 to 99 mol%. When the proportion of the ethylene structural unit is less than 65 mol%, the softening point of the acrylamide copolymer becomes low, and tackiness such as tack and stickiness occurs at high temperature or high humidity, which causes blocking. . When it exceeds 99 mol%, the antifogging property of the acrylamide copolymer becomes too small. In the present invention,
The proportion of the ethylene structural unit is particularly preferably 85 to 97 mol% from the viewpoint of the balance between blocking and antifogging properties.

The general formula in the acrylamide-based copolymer:

[Chemical 11] The ratio of the acrylate structural unit represented by the formula (wherein R ¹ is the same as above) is 0 to 15 mol%. When the ratio of the acrylate structural unit is more than 15 mol%, the softening point of the acrylamide copolymer becomes low and blocking due to tackiness such as tack and stickiness occurs. In the present invention, when the acrylamide-based copolymer contains an acrylate structural unit, the film-forming ability is increased, as a result, the adhesiveness to the base film is increased, and the durability of the antifogging effect is increased. It is preferable because it increases. In the present invention, the proportion of the acrylate structural unit is preferably 1 to 15 mol%, and more preferably 3 to 7 mol%, from the viewpoint of the balance between blocking and endurance.

In the acrylate structural unit, R ¹
Is an alkyl group having 1 to 4 carbon atoms. Specific examples of R ¹ include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group and an i-butyl group, and these groups are mixed in one molecule. May be. Among these groups, the methyl group and the ethyl group are preferable from the viewpoint of not causing any adverse effect due to adhesiveness.

The general formula in the acrylamide-based copolymer:

[Chemical 12] (In the formula, R ² , R ³ , R ⁴ and R ⁵ are the same as above), and the proportion of the acrylamide structural unit is 1 to 35 mol%. The proportion of acrylamide structural units is 1 mol%
If it is less than 3, the antifogging property becomes too small, and also 3
When it exceeds 5 mol%, the acrylamide-based copolymer becomes hygroscopic, and tacking-based blocking occurs under high temperature and high humidity. In the present invention, the proportion of the acrylamide structural unit is particularly preferably 3 to 15 mol% from the viewpoint of balance between antifogging property and blocking property.

In the acrylamide structural unit, R
² is an alkylene group having 2 to 8 carbon atoms. R like this
Specific examples of ² include an ethylene group, a propylene group, a hexamethylene group, and a neopentylene group, and these groups may be mixed in one molecule. Among these groups, an ethylene group and a propylene group are preferable, and a propylene group is particularly preferable, from the viewpoint of easy production and economy.

R ³ and R ⁴ are each 1 to 1 carbon atoms.
4 is an alkyl group. Specific examples of R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group, and a butyl group, and these groups may be mixed in one molecule. Among these groups, a methyl group and an ethyl group are preferable from the viewpoint of antifogging property.

R ⁵ is an alkyl group having 1 to 12 carbon atoms,
Arylalkyl group having 6 to 12 carbon atoms or 6 to carbon atoms
12 is an alicyclic alkyl group. Specific examples of R ⁵ include alkyl groups such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, n-octyl group and n-lauryl group. Examples include groups; arylalkyl groups such as benzyl group and 4-methylbenzyl group; alicyclic alkyl groups such as cyclohexyl group and methylcyclohexyl group, and these groups may be mixed in one molecule. In addition, as said R ⁵ ,
A linear alkyl group and an arylalkyl group are preferable from the viewpoint of tackiness, and a lower alkyl group is preferable from the viewpoint of antifogging property. Particularly preferred R ⁵ includes a methyl group and an ethyl group.

The X is, for example, a halogen atom such as Cl, Br or I, CH ₃ OSO ₃ or C ₂ H ₅ OSO ₃ , and these may be mixed in one molecule. In addition,
Among these, Cl, CH ₃ OSO ₃ from the viewpoint of antifogging property.
And C ₂ H ₅ OSO ₃ are preferred.

The acrylamide copolymer used in the present invention has a weight average molecular weight of 1,000 to 50,000. The term "weight average molecular weight" as used herein means a polystyrene-equivalent weight average molecular weight measured by gel permeation chromatography, and is based on ultrahigh temperature GPC (Kinukawa, Kobunshi Kobun, Vol. 44, No. 2, 139-141). (19
1987)). When the molecular weight is less than 1,000, the film-forming ability is poor and the antifogging effect, which is the object of the present invention, cannot be sufficiently exhibited. On the other hand, when it exceeds 50,000, the viscosity of the aqueous composition becomes too large, resulting in poor workability. A preferred weight average molecular weight is 3,000 to 30,000.
It is 0.

The acrylamide-based copolymer used in the present invention is, for example, an ethylene-acrylic acid ester copolymer obtained by copolymerizing ethylene and an acrylic acid ester by a high-pressure polymerization method, as disclosed in, for example, JP-A-60-79008. The ethylene-acrylic acid ester-acrylic acid copolymer thus obtained was hydrolyzed at the same time as hydrolysis to obtain a desired molecular weight by the method described, and the obtained ethylene-acrylic acid ester-acrylic acid copolymer was amidated with N, N-dialkylaminoalkylamine and then quaternized It is obtained by cation modification with an agent. The acrylamide copolymer thus obtained is blended with the raw material resin of the film, and the T-die method,
It can be carried out by molding by a known film molding method such as an inflation method.

Method for Preparing Aqueous Solution of Acrylamide Copolymer On the other hand, when the acrylamide copolymer is used as a coating type antifogging agent, it is convenient to prepare it in advance as an aqueous composition. The composition can be easily prepared, for example, by a high-pressure emulsification method, that is, by charging an acrylamide copolymer and water into an autoclave, stirring the mixture at a temperature of 110 to 140 ° C. under pressure, and emulsifying or dispersing the composition.

Material of film for imparting antifogging property Polyvinyl chloride, polyvinylidene chloride, EVA (ethylene-vinyl acetate copolymer), low density polyethylene, high density polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyamide 6-6 , Polycarbonate, etc. can be exemplified.

Among these, polyvinyl chloride, polyvinylidene chloride, low density polyethylene, polystyrene, polyethylene terephthalate, polyamide 6-6, polycarbonate and the like are preferable in the coating type.

In the kneading type, EVA, low density polyethylene, high density polyethylene, polypropylene, polyamide 6-6 and the like are used.

Compounding amount in case of kneading type: 3 to 30 parts, preferably 5 to 2 based on 100 parts of raw material resin.
Add 0 parts.

If the amount is less than 3 parts, the antifogging effect is insufficient and 3
If it exceeds 0 parts, physical properties such as strength of the film may be deteriorated.

As a coating method, known methods such as a roll coater and a knife coater can be used.

The thickness of the dried coating film is 1 to 30 μm,
The effect is large when the thickness is preferably 3 to 10 μm.

If it is less than 1 μm, the antifogging effect and durability are insufficient, and if it exceeds 30 μm, it is uneconomical.

Use of anti-fog plastic film The anti-fog plastic film obtained by the present invention is
It can be used for agricultural greenhouses, food packaging, miscellaneous goods packaging, etc.

[0031]

[Operation] In the acrylamide copolymer used in the present invention, it is considered that the hydrophilic cationic acrylamide structural unit introduced into polyethylene imparts hydrophilicity to the plastic film and exerts an antifogging effect.

Further, unlike a low molecular weight anti-fog agent, since it adheres firmly to the plastic film or to the surface, it has excellent durability.

[0033]

EXAMPLES Synthesis of the acrylamide copolymer used in the present invention was carried out according to the following production examples.

<Production Example 1> 400 ml of xylene, ethylene-ethyl acrylate-acrylic acid copolymer (in a 1-liter four-necked flask equipped with a thermometer, a stirrer, a dropping funnel and a Dean-Stark water diverter ( 150 g of ethylene / ethyl acrylate / acrylic acid = 93/3/4) and 1.0 g of paratoluenesulfonic acid were charged.

Next, 21.1 g of N, N-dimethylaminopropylamine was charged and the temperature was adjusted to 140 ° C. using an oil bath.
The mixture was heated to 1, the water formed was continuously removed by azeotropy with xylene, and the mixture was further reacted at 140 ° C. for 17 hours, and the amidation reaction was continued until no water was formed and no water azeotropy was observed. .

458 g of the obtained reaction product was cooled to 80 ° C., and methyl iodide 2 was added to the reaction mixture from a dropping funnel.
8.7 g was gradually added dropwise over 1 hour. During this time, an exotherm was observed, but the reaction temperature was lowered to 90 ° C by cooling.
Maintained at. After completion of dropping, an aging reaction was carried out at 100 ° C. for 4 hours. The reaction product thus obtained was poured into a large amount of methanol, and the generated precipitate was collected and dried to obtain an acrylamide copolymer. The weight average molecular weight of the acrylamide copolymer was measured to be 1
It was 9,400.

<Production Examples 2 to 9> In the same manner as in Production Example 1, the acrylamide copolymers shown in Production Examples 2 to 9 in Table 1 were prepared according to the method described in Japanese Patent Application No. 2-331082. Manufacturing Examples 2 to 9 differ from Manufacturing Example 1 in the following points.

In Production Examples 8 and 9, R ¹ in the ethylene-ethyl acrylate-acrylic acid copolymer of the raw material copolymer was n-propyl group and n-butyl group, respectively. An ethylene-acrylic acid copolymer was used as the polymer.

In Preparation Examples 4 and 8, N, N-dimethylaminoethylamine was used as the aminating agent, and Preparation Example 6
In the production example 7, N, N-dimethylaminoneopentylamine was used as the aminating agent.
N-diethylaminopropylamine was used, and in Production Example 9, N, N-diethylaminoethylamine was used as the aminating agent. Further, in Production Examples 2, 5, 6 and 8, diethyl sulfate was used as the quaternizing agent, in Production Examples 4 and 9, benzyl chloride was used as the quaternizing agent, and in Production Example 3, p-methyl was used as the quaternizing agent. Benzyl chloride was used.

Table 1 shows R ^{1 to} R ⁵ and X ⁻ in each structural unit of the acrylamide copolymers of Production Examples 1 to 9, the content of each structural unit, and the weight average molecular weight.

[0041]

[Table 1] Preparation of the aqueous composition of the acrylamide copolymer was performed as follows.

The acrylamide copolymer obtained as described above was heated in an autoclave at 120 ° C. and 2 to 2.5 kg /
Stirring is continued for 2 hours at a pressure of cm ² and a solid content of 20%.
An aqueous composition of

The aqueous composition obtained above was used in the following examples to obtain plastic films. In addition, Examples 1 to 9 are coating type, and Examples 10 to 14 are kneading type.

(Examples 1 to 9) The aqueous compositions obtained above were diluted with water to a solid content concentration of 5%, and the results are shown in Table 2.
The base film (thickness: 50 μm) described in 1 above is coated with a roll coater so that the thickness after drying is 7 μm,
It was dried at 110 ° C. for 5 minutes. In the case of low density polyethylene, it was dried at 80 ° C for 10 minutes.

Using the obtained film, antifogging property, its durability, transparency and blocking resistance were examined, and the results are shown in Table 2. The test method and evaluation criteria are as follows.

(A) Transparency The transparency of the film coated with the acrylamide copolymer of the present invention was visually evaluated.

◯: Good transparency x: Poor transparency (b) Blocking resistance Two films coated with the acrylamide copolymer of the present invention were sandwiched between 20 cm × 20 cm glass plates and 40 ° C.
In an oven, and aged for 14 days. After 14 days, the film was taken out, peeled off by hand, and checked for blocking.

◯: No blocking X: Blocking (c) Antifogging effect and its sustainability [Initial antifogging property] 300 ml of water was put into a 500 ml beaker, and an aqueous composition of acrylamide copolymer was applied and dried. The beaker was immersed in a constant temperature water bath at 50 ° C. after covering the upper part with the film and sealing it. After 1 hour, the inner surface of the film was observed to evaluate the degree of water droplet attachment.

◯: No fogging is observed.

Δ: Slightly cloudy.

X: There is cloudiness and the contents cannot be seen.

[Persistence of anti-fogging effect] Similarly, a beaker covered with a coating film was provided with a constant temperature water bath of 40 ° C., and the temperature of the atmosphere was kept constant in an oven which was repeatedly cycled at 20 ° C. for 8 hours and 0 ° C. for 16 hours. It was dipped in a water tank and the number of days until the antifogging effect on the film surface disappeared was examined.

As a comparative test, the following tests and evaluations were carried out using the following conventionally used antifog agents.

Comparative Example 1: Sorbitan Monostearate Comparative Example 2: Sorbitan Monooleate

[Table 2] (Examples 10 to 14) A predetermined amount of the acrylamide copolymers obtained in Production Examples 2 and 8 was mixed with the resins shown in Table 3 to obtain T.
Molded into a film having a thickness of 50 μm by a die method, and
It evaluated similarly to 9. The results are shown in Table 3.

As a comparative test, the following tests and evaluations were carried out using the following conventionally used antifog agents.

Comparative Example 3: 1 part of sorbitan monostearate to 100 parts of resin Comparative Example 4: 1 part of sorbitan monooleate to 100 parts of resin

[Table 3] As is clear from the results shown in Tables 2 and 3, Example 1
In all of Nos. 14 to 14, a plastic film having good transparency and free from blocking was obtained, and the antifogging property and its durability were also good. In particular, the antifogging durability was remarkably improved as compared with the conventional product.

The antifogging method of the present invention can be applied to various resin molded products other than plastic films.

[0058]

As described above, the anti-fogging plastic film obtained by the present invention does not cause whitening or blocking, and its anti-fogging effect has excellent durability.

Further, the antifogging method of the present invention is simple, and in the coating type, since an aqueous medium is used, there is no danger of catching fire during processing.

Claims (4)

[Claims] 1. A plastic film having the formula: An ethylene structural unit represented by the formula: 65 to 99 mol%, the general formula: (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms), the acrylate structural unit is represented by 0 to 15 mol% and the general formula: (In the formula, R ² is an alkylene group having 2 to 8 carbon atoms, R ³ and R ⁴ are respectively alkyl groups having 1 to 4 carbon atoms, R ⁵ is an alkyl group having 1 to 12 carbon atoms, and 6 to 12 carbon atoms. An arylalkyl group or an alicyclic alkyl group having 6 to 12 carbon atoms, X
Is a halogen atom, CH ₃ OSO ₃ or C ₂ H ₅ OSO
Acrylamide structural units 1 to 3 represented by ₃ are shown)
An antifogging plastic film obtained by applying an aqueous composition of 5 mol% of a acrylamide-based copolymer having a weight average molecular weight of 1,000 to 50,000, which is randomly arranged in a linear fashion, and dried. 2. An antifog method for a plastic film, which comprises applying the aqueous composition of the acrylamide copolymer according to claim 1 to a plastic film and drying the composition. 3. A raw material resin 100 for a plastic film.
An antifogging plastic film comprising 3 to 30 parts by weight of the acrylamide copolymer according to claim 1 in parts by weight. 4. A raw material resin 100 for a plastic film.
An anti-fogging method for a plastic film, which comprises blending 3 to 30 parts by weight of the acrylamide-based copolymer according to claim 1 in parts by weight.