JPH0813531B2 - Surface treated polyvinyl alcohol film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a polyvinyl alcohol-based film having improved pro-tacking resistance.

B. Conventional Technology Polyvinyl alcohol (hereinafter abbreviated as PVA) film is widely used as various packaging materials because it has excellent transparency and surface gloss and exhibits excellent toughness, but it is poor in slipperiness, so the film It tends to stick to each other and cause a so-called blocking phenomenon, and especially when it is used in an automatic wrapping machine or an automatic bag making machine and operated at high speed, the film wound into a roll is not easily released, and the film adheres to the device. However, there is a drawback that the workability is significantly impaired, and in some cases, the film is broken and it becomes impossible to work.

Therefore, conventionally, silicon dioxide, titanium dioxide, clay,
Although fine powder such as bentonite is applied to the surface of the film, this method reduces the transparency of the film and damages the commercial value, or the powder tends to fall off, and the effect of preventing blocking is sufficient. There are drawbacks that cannot be demonstrated. In general, a method of applying an organic solvent solution of an organic polymer substance to the surface of a synthetic resin film to prevent blocking is also known, but even if the method is applied to a PVA film, it is also used in such a method. Organic polymer substances are usually hydrophobic resins and have poor adhesion to PVA film,
When heat-sealing the treated film, even if the applied resin itself has excellent heat-sealing properties,
The PVA film layer is easily peeled off, and as a result, it is difficult to carry out heat sealing with a strong bonding force, and in this method, it is well known that it is usually used for adhesion of PVA film such as calcium bromide and magnesium nitrate. When the PVA film is adhered by the adhesive of the above, the adhesiveness is remarkably reduced and the application is limited.
It cannot be said that it is a practical method as a method of preventing blocking of A.

In order to improve these, a method has been proposed in which a hydrophobic synthetic resin emulsion such as polystyrene and polyvinylidene chloride is scattered on a PVA film (Japanese Patent Publication No. 56-3861).
No. 0).

However, the adhesion between the emulsion particles and the PVA film is poor, and not only the printing operation, the processing operation such as bag making, the bagging operation, etc., but the anti-blocking ability is deteriorated,
Since the bag sometimes adheres to the packaged contents and changes the color tone, the above method is not yet satisfactory.

In order to solve such a problem, a method of coating a composition comprising a styrene resin emulsion or a methacrylic resin emulsion, a polyvinyl alcohol aqueous solution, a silicone water repellent, and an aqueous dispersion of fine particles having a specific particle size. Has been proposed (JP-A-57-92031). However, this method is not only complicated in the preparation of the coating solution, but also the transparency, the blocking resistance, the heat sealability of the PVA film and the property that the coated material does not fall off during processing such as printing and bag making (rub resistance). ) Can not be satisfied at the same time, and at present it cannot be said that it is a satisfactory method.

C. Problem to be Solved by the Invention It is an object of the present invention to provide a surface-treated polyvinyl alcohol film which does not have the above problems at all.

D. Means for Solving the Problems The inventors of the present invention have conducted extensive studies to improve the above-mentioned drawbacks, and as a result, using polyvinyl alcohol as a binder, methyl methacrylate (A having a specific composition having a specific particle diameter) ) / Styrene (B) / monomer (C) having a functional group on at least one side, a surface-treated polyvinyl alcohol-based film having a specific amount fixed on at least one side does not impair the transparency of the film, and the film is blocked. Not only can the phenomenon be markedly reduced, but the heat-sealing properties of the PVA film, calcium bromide, magnesium nitrate, etc.
The PVA film is attached to an automatic packaging machine, an automatic bag-making machine, etc. for bonding and various processing such as bag-making without damaging the properties such as the adhesiveness of the film by the adhesive that is usually used for the film. The present invention has been completed by finding that it is possible to carry out the above-mentioned process and that no lost objects are generated at that time.

That is, the present invention uses polyvinyl alcohol as a binder, and uses 40 to 80% by weight of methyl methacrylate (A).
Vinyl monomer (C) having 20 to 60% by weight of styrene (B) and at least one functional group selected from functional groups of hydroxyl group, carboxyl group, amide group and amino group
0.5 to 20% by weight of copolymer having an average particle diameter of 0.02 to 1 μm
Copolymer particles of at least one side, 0.01 per side
It is a surface-treated polyvinyl alcohol-based film in which ~ 0.2 g / m ^{2 is} immobilized.

 Hereinafter, the present invention will be described in detail.

As the PVA film to be used in the present invention, first, PVA obtained by saponifying polyvinyl acetate is a water-soluble PVA film produced by a known film forming method such as a solution casting method and a melt extrusion method. Examples thereof include a film or a so-called vinylon film which is made water-insoluble or water-insoluble by further heat treatment or water resistance treatment such as formalization or acetalization of the film. The degree of polymerization of PVA and the degree of saponification are not particularly limited, but the degree of polymerization is usually 500 to 3000, preferably 1000 to 2000, and the degree of saponification is 75 mol% or more, preferably 85 mol% or more. It is preferably used because it is excellent in strength and gas impermeability.

Therefore, the PVA film to be used in the present invention is not only a film produced by forming a film of PVA obtained by saponifying the above-mentioned polyvinyl acetate, but also an ethylenic vinyl copolymerizable with vinyl acetate. Saturated monomers such as crotonic acid,
Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc., or their alkyl esters, vinyl chloride, vinylidene chloride, acrylamide, acrylonitrile or alkyl vinyl ethers, small amounts of ethylene, propylene and other α-olefins, etc. A film obtained from a modified PVA such as a saponified product of a polyvinyl acetate copolymer containing as a copolymerization component, or a film obtained by heat-treating or insolubilizing the film is also included.

Further, the PVA film used in the present invention includes a sheet having a thickness of 5 mm or less, but a sheet having a thickness of 5 to 200 μm is usually preferably used.

Examples of the vinyl monomer (C) having the functional group include the following.

Examples of vinyl monomers having a hydroxyl group include 2-hydroxy acrylate, 2-hydroxy methacrylate, allyl alcohol, and methylol acrylamide, and examples of vinyl monomers having a carboxyl group include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, Itaconic acid monoalkyl ester, fumaric acid monoalkyl ester, maleic acid monoalkyl ester are exemplified, amide group-containing monomers include acrylamide, methacrylamide, and N-vinylpyrrolidone, and amino group-containing monomers include vinylpyridine. Is mentioned. Among these (C) components, a copolymer having a monomer having a hydroxyl group as one component is particularly preferable.

Methyl methacrylate (A) used in the present invention,
The copolymerization composition of styrene (B) and the copolymer of vinyl monomer (C) having at least one functional group among hydroxyl group, carboxyl group, amide group and amino group is
A copolymer composition of (A) component 40 to 80% by weight, (B) component 20 to 60% by weight and (C) component 0.5 to 20% by weight,
Component (A) 50 to 70% by weight, component (B) 30 to 50% by weight and component (C) 1 to 15% by weight are more preferred copolymerization compositions.

Regarding the copolymer composition, methyl methacrylate (A) needs to be 40 to 80% by weight and styrene (B) to 20 to 60% by weight. If a copolymer outside this range is used, the film becomes transparent. It may impair the sex.

Further, when the composition of the vinyl monomer (C) having the functional group is 0.5% by weight or less, the blocking resistance is deteriorated, and when it is 20% by weight or more, the particles easily fall off due to the friction on the surface of the film when it is used in an automatic bag making machine or the like. That is, the so-called abrasion resistance is likely to decrease.

In the present invention, it is important to select the particle size of the copolymer particles, and it is necessary to use particles having a particle size in the range of 0.02 to 1 μm. A more preferable particle size is 0.05 to 0.2 μm. If the average diameter is less than 0.02 μm, the blocking resistance is lowered, while if it exceeds 1 μm, the transparency of the film is lowered, which is inconvenient.

The copolymer particles may be those obtained by various methods prepared by a physical method such as pulverizing the copolymer to a predetermined size, but it is particularly economical to use emulsion obtained by emulsion polymerization or the like. Is advantageous.

Further, the emulsion mentioned above can exert a sufficient anti-blocking effect when used alone, but if necessary, other anti-blocking agents such as silicon oxide, titanium dioxide, clay, bentonite, stearic acid and its salts or amides can be added. It can be used together appropriately.

Further, the polyvinyl alcohol film of the present invention comprises a methylmethacrylate (A) / styrene (B) / functional group-containing monomer (C) copolymer particle having an average particle size of 0.02 to 1 μm, at least on one side and 0.01 per side. ~ 0.2 g / m ² .

If it is less than 0.01 g / m ² , sufficient blocking property cannot be obtained,
^{On the other hand} , if it exceeds 0.2 g / m ² , heat sealability and glue sealability will be poor, which is not preferable.

Further, the methyl methacrylate (A) / styrene (B) / functional group-containing monomer (C) copolymer particles of the present invention having an average particle diameter of 0.02 to 1 μm are provided on at least one side and 0.01 per side.
The method for producing the surface-treated polyvinyl alcohol-based film, which has a content of ~ 0.2 g / m ² , does not have any limitation, but a suitable production method is, for example, the above-mentioned one having an average particle diameter of 0.02 to 1 µm. copolymer particles, preferably the copolymer Emarujiyon which is obtained by emulsion polymerization or the like, a polyvinyl alcohol as a binder, be obtained by 0.01~0.2g / m ² coated and dried as per one side copolymer particles solids it can.

In the above-mentioned preferred production example, in coating the copolymer particles, preferably the copolymer emulsion on a polyvinyl alcohol film, polyvinyl alcohol (hereinafter abbreviated as PVA) is required to be used as a binder. There is. If you don't use a binder,
Even if a little friction is applied to the surface of the film, the particles are likely to come off, and if a binder other than PVA is used, the adhesive strength to the base polyvinyl alcohol film is low and the coat layer easily comes off.

The PVA is a water-soluble PVA having a saponification degree of 80 mol% or more.
The polymerization degree is not particularly limited, and the average polymerization degree is 100.
In addition to those preferably used up to 4000, ethylenically unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, maleic acid and itaconic acid or their alkyl esters, vinyl chloride, vinylidene chloride, acrylamide, acrylonitrile or alkyl. A modified PVA such as a saponified product of a polyvinyl acetate copolymer containing a small amount of α-olefin such as vinyl ether, alkoxy vinyl silane, ethylene or propylene as a copolymerization component can also be preferably used.

The ratio of PVA and emulsion used when applying the emulsion is not particularly limited, but PVA / emulsion (fixed weight ratio) is 20/1 to 1/20, preferably 5 /
The range of 1 to 1/2 is preferred.

The concentration of these coating liquids is not particularly limited, and an appropriate concentration should be selected according to the coating amount, but in consideration of the drying process and workability, the total solid content is usually 0.05 to 5
%, Preferably 0.1 to 3% is suitable.

As a method of applying the emulsion and PVA to the surface of the PVA film, any known method such as a roll coater method, an air doctor method, a blade coater method, a spray method, a dipped method, etc. can be adopted.

In performing the coating of the present invention, it is necessary to keep the film under tension because the PVA film swells with the coexisting water.

After carrying out the coating of the present invention, the film is dried by a conventional method. The drying temperature is not particularly limited, but if it is less than 30 ° C, not only is the film prone to wrinkles and irregularities, but it also takes a long time to dry and is not practical.
It is usually 30 because higher temperature causes film shrinkage and deterioration.
It is suitable to select from the range of up to 160 ° C.

The present invention can be applied to one side or both sides of the sheet-shaped film as described above, but is not limited to this, and also for the tube-shaped film obtained by the inflation method, It is suitable to keep the film under tension and apply the coating liquid of the present invention to the inside of the tube by a spray method or the like. Also, if necessary, not only the inner surface of the tube-shaped film but also the outer surface thereof can be subjected to anti-blocking treatment.

E. Examples The present invention will be described in more detail with reference to the following examples. Hereinafter, "part" or "%" is based on weight unless otherwise specified.

Example 1 After dissolving 0.8 parts of sodium dodecylbenzenesulfonate in 100 parts of water in a reactor equipped with a stirrer, 22.8 parts of methyl methacrylate (MMA), 15.2 parts of styrene (St) and 2 parts of 2-hydroxyethyl acrylate (HEA) were dissolved. Then, emulsion polymerization was performed at 70 ° C. using ammonium persulfate to obtain emulsion having an average particle size of 0.1 μm.
(I)] was obtained.

Then, emulsion (I) was added to a 2% aqueous solution of PVA having an average degree of polymerization of 1700 and a degree of saponification of 99.2 mol% so that PVA / emulsion (solid content) = 1/1 to obtain a coating solution, which was used as a roll coater. Then, apply it to a PVA film with a thickness of 30 μm so that it will be 0.03 g / m ² in terms of solid content in emulsion.
It was dried with hot air at ℃ for 2 seconds. Table 1 shows the physical properties of the obtained film. Transparency, blocking resistance, abrasion resistance,
All the physical properties such as heat seal strength and adhesive strength of glue were satisfied.

As a control example, Table 1 also shows the physical properties of the PVA film when the above treatment was not performed.

Examples 2 and 3 The reactor used in Example 1 had an average particle size of 0.10 μm, MMA /
St / acrylic acid (AA) = 58/39/3 emulsion (Example 2) and MMA / St / N-methylol acrylamide (N-MA)
N) = 60/38/2 emulsion (Example 3) was prepared.
A coating solution of PVA / emulsion (solid content) = 1/1 was prepared, and the PVA film used in Example 1 was coated in the same manner as in Example 1 so that the emulsion solid content was 0.02 g / m ^2. Dried. Table 1 shows the physical properties of the obtained PVA film.

Comparative Example 1 The reactor used in Example 1 had an average particle size of 0.10 μm and MMA /
An emulsion of St = 60/40 was prepared, and as in Example 1, P
Table 1 shows the results of coating the PVA film with a coating solution of VA / emulsion (solid content) = 1/1 at a ratio of 0.03 g / m ^{2 in} terms of solid content of emulsion.

Comparative Examples 2 and 3 In Example 1, the emulsion coating amount was changed from 0.03 g / m ²
0.002 g / m ² (Comparative Example 2) and 1.20 g / m ² (Comparative Example 3)
A PVA film was obtained by the same method as in Example 1 except that the PVA film was changed to. The results are shown in Table 1.

Example 4 MMA / St / HEA = 57/38/5, emulsion having an average particle size of 0.05 μm and PVA (average degree of polymerization 1700, degree of saponification 98.5 mol%) were added to P
VA / emulsion (solid content) = 3/1 was mixed to obtain a coating liquid. Table 1 shows the results of coating the PVA film used in Example 1 with an emulsion coating amount of 0.02 g / m ² .

Example 5 MMA / St / HEA = 67/28/5, emulsion having an average particle size of 0.1 μm and PVA (average degree of polymerization 1300, degree of saponification 99.5 mol%) were used as PVA.
/ Emulsion (solid content) = 2/1 was mixed to obtain a coating liquid. Table 1 shows the results of coating the PVA film used in Example 1 with an emulsion coating amount of 0.05 g / m ² .

Example 6 MMA / St / HEA = 57/38/5, emulsion having an average particle size of 0.3 μm was PVA (average polymerization degree 1300, saponification degree 99.5 mol%).
/ Emulsion (solid content) = 2/1 was mixed to obtain a coating liquid. Table 1 shows the results of coating the PVA film used in Example 1 with an emulsion coating amount of 0.10 g / m ² .

Example 7 Emulsion coating amount of Example 1 0.03 g / m ² to 0.01 g / m ²
A surface-treated PVA film was obtained by the same method as in the example except that The results are shown in Table 1.

Example 8 Instead of the emulsion- (I) in Example 1, MM
A / St / 2-Hydroxyethyl Methacrylate (HEMA) = 54
A surface-treated PVA film was obtained by the same method as in Example 1 except that emulsion having a particle size of / 36/10 and an average particle size of 0.10 μm was used. The results are shown in Table 1.

Comparative Example 4 MMA / St / HEA = 57/38/5, emulsion having an average particle size of 1.2 μm and PVA (average degree of polymerization 1700, degree of saponification 99.2 mol%) were mixed in a solid content of 1/1. As a coating solution, an emulsion coating amount of 0.30 g / m ² was applied to obtain a coated PVA film. The results are shown in Table 1.

Comparative Example 5 MMA / St / HEA = 57/38/5, emulsion having an average particle size of 0.015 μm was mixed with PVA (average degree of polymerization 1700, degree of saponification 99.2 mol%) so that the solid content was 1/1. As a coating solution, a PVA film coated with an emulsion coating amount of 0.005 g / m ² was obtained. The results are shown in Table 1.

Comparative Example 6 St / HEA = 95/5, emulsion with average particle size 0.10 μm and PV
A (average degree of polymerization 1700, degree of saponification 99.2 mol%) was mixed at a solid content of 1/1 to form a coating solution, and the emulsion coating amount was 0.03 g / m ² and the coated PVA film was coated. Obtained. The first result is displayed.

Comparative Example 7 A coated PVA film was obtained under the same conditions as in Example 1 except that the PVA binder was not used. The results are shown in Table 1.

As described above, when the conditions of the present invention are not satisfied, it is understood that all the required physical properties are not satisfied, and cannot be put to practical use.

1) MMA; methyl methacrylate, St; styrene, HEA; 2
-Hydroxyethyl acrylate, AA; acrylic acid, N
-MAM; N-methylol acrylamide, HEMA; 2-hydroxyethyl methacrylate 2) Transparency was represented by the number of 9-point type printable through the stacked films. (Film thickness is 30μm per sheet) 3) About blocking resistance, about 50 sheets of 10cm × 10cm size are stacked, and a load of 80g / m ² is applied on top of them, at 80 ℃, 80%
After being left in an RH atmosphere for 24 hours, the adhesion between the films was evaluated by a tensile tester by T peel strength (g / 10 cm).

4) As for abrasion resistance, a 1 kg jig with black cotton velvet attached to the outer surface of a cylinder with an outer diameter of 32 mm and a width of 24 mm was used on the film.
The sensory evaluation was performed by sliding without rolling over a length of 0 cm and by the amount of fine powder deposited on the velvet.

A: No fine powder is attached.

B: Fine powder is attached, but there is a very small amount.

C: A large amount of fine powder is attached.

5) Heat seal strength is Fuji Impulse Sealer FI-
24 at 20 ℃ -65% RH by 600 type (manufactured by Fuji Manufacturing Co., Ltd.)
Heat-seal the PVA film whose humidity has been adjusted, and measure the sealing strength per 15 mm width with a tensile tester.

6) Adhesive strength is 20 parts of lithium chloride, 32 parts of water, 48 parts of methanol. A solution of lithium chloride is applied to a PVA film at 20 ° C and 65% RH, and another PVA film is attached. Measure the adhesive strength per 15 mm width after leaving for a period of time with a pulling tester.

Comparative Example 8 A surface-treated PV was prepared in the same manner as in Example 1 except that the emulsion and coating conditions shown in Table 2 were used instead of the emulsion and coating conditions used in Example 1.
I got an A film. The results are shown in Table 2.

F. Effects of the Invention As is apparent from the above examples, the surface-treated polyvinyl alcohol of the present invention has transparency, blocking resistance, abrasion resistance, heat seal strength and adhesive strength as compared with the conventional polyvinyl alcohol film. All of the strengths are extremely excellent, and the industrial value is extremely high.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location C08F 216/04 MKV 220/04 MLU 8619-4J 220/28 MMN 220/56 220/58 MNG 226 / 06 MNM 226/10 MNN

Claims (2)

[Claims] 1. Using polyvinyl alcohol as a binder, methyl methacrylate (A) 40 to 80% by weight, styrene (B) 20 to 60% by weight and functional groups of hydroxyl group, carboxyl group, amide group and amino group. Vinyl monomer (C) 0.5-20 having at least one selected functional group
% Of copolymer particles having an average particle size of 0.02 to 1 μm, which is 0.01% to 0.2 g / m on each side, on at least one side.
² Immobilized surface-treated polyvinyl alcohol film. 2. Using polyvinyl alcohol as a binder, the emulsion of the copolymer particles according to claim 1 on at least one side, and 0.01 to 0.2 g / m ^{2 in} terms of solid content per one side.
A method for producing a surface-treated polyvinyl alcohol film, which comprises drying after coating.