JPH042429B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a slippery polyester film,
More specifically, the present invention relates to a slippery polyester film comprising a slippery thin layer of a methacrylate copolymer provided on at least one side of the polyester film. <Prior art> Polyester films, especially biaxially stretched films of polyethylene terephthalate, have excellent mechanical properties, heat resistance, chemical resistance, etc.
The demand for it as a material for magnetic tape, food film, packaging film, metallizing film for capacitors, electrical insulation film, OHP film, etc. has been growing particularly rapidly recently. However, in order to smoothly produce polyester films and apply them to the above-mentioned uses, it is necessary to improve the slipperiness of polyester films. In other words, especially in the case of a polyester film with a flat surface, the slipperiness of the film is insufficient and it is difficult to wind it up.
This seriously impedes the work of winding, coating, slitting, etc., and causes problems such as wrinkles in the winding and dust adsorption due to the generated static electricity. for example,
When various molded products made by applying pressure molding or vacuum forming to unstretched or uniaxially stretched polyethylene terephthalate films are stacked on top of each other, the molded products can be smoothly pulled out from each other if surface activity is insufficient. Therefore, the ease of assembly line work in the processing process is significantly reduced. Conventionally, as a means to improve the slipperiness of polyester films, films are formed using polyester to which microparticles of various fillers such as silicon oxide, kaolin, talc, calcium carbonate, or alumina are added, followed by a biaxial stretching process. It has been put into practical use to utilize the phenomenon in which fillers protrude as minute protrusions from the film surface when the film thickness decreases. Similarly, as a technique for improving slipperiness using microprotrusions, a method is also known in which a catalyst used during polyester polymerization is converted into particles insoluble in the polymer. Although these methods have been successful in improving the slipperiness of the film, the presence of small particles within the film composition naturally reduces the transparency of the film or introduces voids within the film composition. There are still issues that need to be improved, such as generation. In particular, the reduction in transparency or the formation of voids in polyester films used as materials for diazo films, metallized films, photographic films, and magnetic tapes and floppy disks that require flattening of the base surface due to high density is a serious problem. It becomes an obstacle. On the other hand, unlike the above method in which microparticles are added to polyester to form microprotrusions on the film surface, a method in which a specific coating liquid is applied to both sides of a film made from polyester that does not contain such microparticles is used. Accordingly, a method has been proposed in which a worm-like film structure is formed on both sides of the film to impart slipperiness to the film. This method uses a specific coating solution containing at least one of silicone or cellulose resin and a water-soluble polymer compound, but in order to impart slipperiness to the film through post-treatment, fine particles are added to the polyester. This is different from the method of adding slippery to the film. However, the water-soluble polymer that creates such a worm-like treated surface has poor adhesion to the polyester film, and a new problem has arisen in that part of the treated layer is scraped off during the coating process or during turning. <Object of the invention> The object of the present invention is to solve this problem, to provide a polyester film with excellent adhesion between a polyester film and a slippery thin layer, and wherein the slippery thin layer has self-fold-like fine irregularities; It is an object of the present invention to provide a polyester film exhibiting excellent slipperiness and preferably excellent durability. <Configuration and Effects of the Invention> According to the present invention, an object of the present invention is to coat methyl methacrylate A, ethyl methacrylate B, and vinyl monomers copolymerizable therewith (however, alkyl (excluding acrylates) and their quantitative ratios are as follows: ]) /([A]+[B]+[C]))≦1.415...(2) [In the formula, [A] is the mole% of the A component in the polymer, and [B] is the mole% of the A component in the polymer. Achieved by an easily slippery polyester film provided with an easily slippery thin layer of a methacrylate copolymer that satisfies the following: mol% of component B, [C] is the mol% of the above component C in the polymer. be done. The easily slippery thin layer forms a continuous layer with respect to the polyester film, and has self-fold-like fine irregularities formed on the surface (the side opposite to the polyester film). An example of such a surface condition is shown in FIGS. 1 and 2. FIG. 1 is an enlarged plan view, and FIG. 2 is an enlarged sectional view. In FIG. 1, the black portions indicate fine irregularities or concave portions, and the white portions indicate concave portions or continuous layer portions. In addition, the convex portion is long in the machine axis direction (longitudinal direction) of the polyester film,
forming folds. In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate,
Examples include poly(1,4-cyclohexylene dimethylene terephthalate) and polyethylene-2,6-naphthalene dicarboxylate, and also include copolymers thereof or blends thereof with small proportions of other resins. The polyester film of the present invention can be obtained by melt-extruding such a linear saturated polyester resin, forming it into a film by a conventional method, and subjecting it to oriented crystallization and heat treatment crystallization. This polyester film has crystal orientation to such an extent that the heat of crystal fusion measured by a differential scanning calorimeter in a nitrogen stream [at a heating rate of 10°C/min] is usually 4 cal/g or more. Preferably. In the present invention, the methacrylate copolymer that forms a slippery thin layer on a polyester film includes methyl methacrylate A, ethyl methacrylate B, and vinyl monomers copolymerizable with these (excluding alkyl acrylates). )C, and their quantitative ratio is the following formula (1), (2) 1<[A]/[B"≦9...(1) 0.75≦((1.5[A]+[B])/ ([A]+[B]+[C]))≦1.415...(2) Here, [A] is the mol% of the A component in the polymer, and [B] is the mol% of the B component in the polymer. %, [C] is a methacrylate copolymer that satisfies the mole % of the C component in the polymer.
In the above formula, if [A]/[B] is less than 1, it will not be possible to exhibit easy sliding properties, while if [A]/[B] exceeds 9, adhesiveness and flexibility will decrease, The abrasion resistance deteriorates, and (1.5[A]+
[B])/([A]+[B]+[C]) (hereinafter referred to as X)
When is less than 0.75, blocking resistance decreases,
On the other hand, if X exceeds 1.415, it becomes difficult to prepare a uniform coating solution, especially a uniform aqueous coating solution, which is not preferable.
Preferably, X is greater than 0.94 and less than or equal to 1.38. Examples of the vinyl monomer C include alkyl methacrylate (the alkyl group is _C3 or higher, n-propyl group, isopropyl group, n-propyl group,
butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); Acrylamide, methacrylamide, N-methylmethacrylamide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-alkoxymethyl(meth)acrylamide (alkyl groups include methyl, ethyl, propyl group, butyl group, isobutyl group, etc.), N,N-dimethylolacrylamide, N
- Amide group-containing monomers such as methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-phenylacrylamide, etc.; amino group-containing monomers such as N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate, etc. Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, etc.; styrene sulfonic acid, vinyl sulfonic acid and their salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.), etc. Monomers containing sulfonic acid groups or their salts such as crotonic acid, itaconic acid, acrylic acid, maleic acid, fumaric acid and their salts (sodium salts, potassium salts, ammonium salts, tertiary amino acids, etc.) Monomers containing carboxyl groups or salts thereof, such as; Monomers containing acid anhydrides such as maleic anhydride, itaconic anhydride, etc.; Others, vinyl isocyanate, allyl isocyanate, styrene, vinyl methyl ether, vinyl Ethyl ether, vinyl tris alkoxysilane, alkyl maleic acid monoester,
Acrylonitrile, methacrylonitrile, alkyl itanconic acid monoester, vinylidene chloride,
Examples include vinyl acetate and vinyl chloride. These can be used alone or in combination of two or more. Among these, hydroxyl groups, amide groups, carboxyl groups, or their salts (sodium salts, potassium salts) , ammonium salt, tertiary amine salt, etc.) are preferred. Furthermore,
From the point of introducing a crosslinked structure into the polymer, N-
Methylol (meth)acrylamide, N-alkoxymethyl (meth)acrylamide, glycidyl (meth)acrylate, (meth)acrylic acid, 2-
Those having a functional group such as an alkoxy group, a methylol group, a carboxyl group, a hydroxyl group and/or an epoxy group, such as hydroxyethyl (meth)acrylate, are preferable. When two types of functional groups are combined, for example, a methylol group and a carboxyl group, a glycidyl group and a hydroxyl group, a glycidyl group and a carboxyl group, etc. can be mentioned. The precursor methacrylate copolymer having these two types of functional groups is a self-crosslinking type. Further, the precursor methacrylate copolymer having one type of functional group is preferably used in combination with a compound having a group with which the functional group reacts or an oligomer thereof (thermosetting agent). As such a thermosetting agent, for example, methylolated melamine resin, epoxy compound, aziridine compound, polyvalent metal compound, etc. are preferably used. The amount thereof is preferably 1 to 30% by weight, more preferably 5 to 15% by weight of the resin solid content forming the easily slippery thin layer. The easily slippery thin layer in the present invention can be formed by applying a coating liquid, preferably an aqueous liquid, containing the components for forming the thin layer onto a polyester film, and drying and curing the coating liquid. When the thin layer-forming component is of a crosslinking type, it is preferable to carry out a crosslinking reaction in the dry curing treatment described above. The coating liquid is preferably an aqueous liquid such as an aqueous solution or a water emulsion liquid. This aqueous liquid may contain some amount of organic solvent to stabilize the dispersion of the solid components.
When an aqueous liquid is used, the precursor methacrylate copolymer forming the methacrylate copolymer or crosslinked copolymer is a hydrophilic polymer. This hydrophilicity can be judged by whether the polymer dissolves in an aqueous medium or forms a uniform emulsion. The aqueous liquid can be produced by any known method. For example, to illustrate an emulsion polymerization method using a water dispersion system for components A, B, and C, an emulsion dispersant (a surfactant such as sodium dodecylbenzenesulfonate) and a water-soluble polymerization initiator (ammonium persulfate) are added to ion-exchanged water. Add an appropriate amount of a polymerization accelerator (a reducing agent such as sodium acid sulfite),
of a given amount of monomer while stirring at a given temperature (e.g. 50-90 °C) and at a given stirring speed and 10-50
% by weight, and once polymerization has started, the addition is interrupted for a short time, the remaining monomers are added at a constant rate, and the emulsion polymerization is carried out under the same conditions for several hours. Aqueous dispersions of the copolymer (or its precursor) can be prepared. At that time, the amount of surfactant used in the reaction added is 5% by weight or less, and more preferably 1 to 1% by weight based on the monomer of the polymerization component.
2% by weight is good. Thus the average particle size of approx.
Fine particles with a particle size of 0.2 μm or less can be obtained. still,
Thermosetting agents, molecular weight regulators (mercaptans), and dispersion aids (polyvinyl alcohol,
Polymer protective colloids such as hydroxymethyl cellulose) etc. may be added. In addition, it is also possible to use a high molecular weight surfactant instead of the above-mentioned low molecular weight surfactant, and to use a production method using so-called soap-free polymerization that does not contain a reactive surfactant. The molecular weight of the methacrylic copolymer (thermoplastic type) or its precursor methacrylic copolymer (crosslinked type) dissolved or finely dispersed in the coating liquid is 1 to 1.
2 million, more preferably 500,000 to 1.5 million. In addition, such polymers have glass transition temperatures of 40°C or higher, and even
The temperature is preferably 50°C or higher. Furthermore, a necessary amount of a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant may be added to the coating liquid, particularly the aqueous solution. As such a surfactant, the surface tension of the aqueous coating solution can be
It is preferable to use a material that can drop to 40 dyen/cm or less and promotes wetting to polyester film, such as polyoxyethylene alkyl phenyl ether,
Polyoxyethylene fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester,
Examples include fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts, and alkyl amine salts. Furthermore, within a range that does not eliminate the effects of the present invention, for example, antistatic agents, ultraviolet absorbers, pigments, organic fillers, inorganic fillers,
Other additives such as lubricants, antiblocking agents, etc. can be mixed. The coating may be carried out in a normal coating process, that is, in a process of coating a biaxially stretched and heat-set polyester film separately from the film manufacturing process. However, this process tends to trap dirt, dust, etc., and it is desirable to apply the coating in a clean atmosphere for advanced products such as magnetic tapes and floppy disks. From this point of view, coating during the polyester film manufacturing process is preferable. In particular, it is preferable to apply an aqueous coating liquid to one or both sides of the polyester film before the crystal orientation is completed during this step. Here, the polyester film before crystal orientation is completed is an unstretched film obtained by thermally melting polyester and forming it into a film as it is; A uniaxially stretched film that is oriented in one direction; and a uniaxially stretched film that is oriented in both the vertical and horizontal directions at a low magnification (before finally being re-stretched in the vertical or horizontal direction to complete oriented crystallization). (biaxially stretched film), etc. The solid content concentration of the coating liquid is usually 30% by weight or less, more preferably 10% by weight or less. The coating amount is preferably 0.5 to 20 g, more preferably 1 to 10 g per m ² of the running film. Any known coating method can be used as the coating method. For example, a roll coating method, a gravure coating method, a roll brushing method, a spray coating method, an air knife coating method, an impregnation method, a curtain coating method, etc. may be applied alone or in combination. The polyester film coated with the coating liquid but before crystal orientation is completed is dried and subjected to processes such as stretching and heat setting. For example, a longitudinally uniaxially stretched polyester film coated with an aqueous solution is guided into a stenter, where it is laterally stretched and heat-set. During this time, the coating solution dries and forms a film having self-folded fine irregularities on the film. Drying is preferably carried out before or during stretching. Conditions for oriented crystallization of the polyester film, such as stretching, heat setting, etc., can be those conventionally accumulated in the art. The easily slippery polyester film of the present invention has excellent adhesion between the easily slippery thin layer and the polyester film, the thin layer does not scrape off, and the surface is flat (for example, surface roughness Ra is 0.02μ or less). It is particularly useful as a base for high-density magnetic tapes, floppy disks, etc. because it has excellent blocking resistance and unwinding properties. <Examples> The present invention will be further explained below with reference to Examples.
Note that "parts" in the examples mean "parts by weight." Moreover, each characteristic of the film was measured by the following method. 1.Surface slipperiness: Easy slippery thin layer surfaces at 20°C and humidity 60%RH.
The coefficient of static friction at a load of 1 kg is measured using a slippery measurement tester manufactured by Toyo Tester Co., Ltd. 2 Blocking property: 10cm x 15cm after aligning the smooth thin layer surfaces.
Cut into squares and store in an atmosphere of 55℃ x 88%RH.
For 17 hours, a weight of 6 kg/cm ² was applied, and then this 10
Measure the peel strength of cm width. The peeling speed at this time was 100 mm/min. 3 Presence or absence of crosslinked structure Five drops of tetrahydrofuran (approx.
0.1cc), place gauze on top, and
Place a 200g weight on it and move the gauze at a speed of approximately 1000mm/min. After drying at room temperature, compare the 400x interference micrographs of those not treated with tetrahydrofuran and those treated with tetrahydrofuran to see changes in the thin layer surface. This state of change is expressed by the following ranks. Thin layer has almost disappeared: × (There is no cross-linked structure) Thin layer morphology has changed: △ (There is a cross-linked structure, but its proportion is small) Thin layer morphology has hardly changed. What is not:
○ (Sufficient crosslinked structure) 4 Surface roughness (Ra) Measured according to JIS S0601. That is, using a stylus-type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd., a film surface roughness curve is drawn on the chart under the conditions of a needle radius of 2 μ and a load of 0.07 g. A part of measurement length L is extracted from the film surface roughness curve in the direction of its center line, and the center line of this extracted part is taken as the X axis, and the direction of vertical magnification is taken as the Y axis, and the roughness curve Y=
When expressed as f(x), the value (Ra: μm) given by the following equation is defined as the film surface roughness. Ra=1/L∫ ^L ₀ |f(x)|dx In the present invention, eight measurements are taken with a reference length of 0.25 mm, and Ra is expressed as the average value of five measurements, excluding three from the largest value. Examples 1 to 4 and Comparative Examples 1 to 3 Polyethylene terephthalate (lubricant) with an intrinsic viscosity of 0.65 measured in O-chlorophenol at 25°C
30 ppm) was melt-extruded onto a rotating cooling drum maintained at 20°C to obtain an unstretched film with a thickness of 950 μm, which was then stretched 3.5 times in the machine axis direction.
An aqueous liquid containing 90 parts of the aqueous resin component shown above and 10 parts of a nonionic surfactant (polyoxyethylene nonyl phenyl ether) was applied to both sides of the uniaxially stretched film by a kiss coating method. Continue horizontally at 105℃
Stretched 3.9 times and further heat treated at 210℃ to a thickness of 75μ
A double-sided easily slippery coated polyester film of m was obtained. The average coating amount at this time is 50 mg/m ² in terms of solid content.
It was hot. The properties of this polyester film are shown in Table 1. Table 1 also shows the performance of polyester films without a slippery layer (30 ppm lubricant, 0.3 wt%) as Comparative Examples 1 and 2.

[Table] It is clear from Table 1 that the polyester film of the present invention is flat and easily slippery, and also has good blocking resistance. Example 5 Water-based resin [MMA/EMA/MAA/HEMA=
80/18/5/3 (molar ratio)] 78 parts, 10 parts of methylolated melamine resin Sumitex Range M-3, 2 parts of Sumitex Accelerator ACX, and 10 parts of a surfactant. A polyester film coated with an easily slipping layer was obtained in the same manner as in Example 1, except for the following. This film has a surface roughness of Ra
It is a flat and slippery film with a coefficient of static friction (μs) of 0.007μ and 0.45.

[Brief explanation of drawings]

FIG. 1 is an enlarged plan view of a slippery polyester film, and FIG. 2 is an enlarged sectional view of the film. In Fig. 2, 1 is the base film, 2
is a slippery thin layer.

Claims (1)

[Claims] 1. On at least one side of the polyester film,
It consists of methyl methacrylate A, ethyl methacrylate B, and a vinyl monomer (however, excluding alkyl acrylate) C that can be copolymerized with these, and the quantitative ratio of these is the following formula (1), (2) 1 < [A ]/[B"≦9...(1) 0.75<((1.5[A]+[B])/([A]+[B]+[C]))≦1.415...(2) [In the formula , [A] is the mole% of the component A in the polymer, [B] is the mole% of the component B in the polymer, and [C] is the mole% of the component C in the polymer. A slippery polyester film comprising a slippery thin layer of a copolymer. 2. The easily slippery polyester film according to claim 1, wherein the methacrylate copolymer has a crosslinked structure.