JP2949738B2 - Manufacturing method of polyvinyl chloride plate with excellent weather resistance - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a polyvinyl chloride plate having excellent weather resistance.

[Prior Art] Polyvinyl chloride resin (hereinafter referred to as RPVC) has transparency and is widely used for various uses. But RP
VC is extremely poor in weather resistance, and it is difficult to drastically solve various additives such as stabilizers. It has a problem that yellowing occurs in a short period of time and, in severe cases, browning.

In order to solve this problem, attempts have been made to form a weatherable coating on the surface of RPVC products. However, RPVC products contain the above-mentioned stabilizers such as metal soaps, and additives such as plasticizers and lubricants such as DOP, which precipitate on the surface and hinder the adhesion of the weather-resistant coating layer. . Therefore, before forming the weather-resistant coating layer by coating, etc., the RPVC product should be washed in advance,
An operation of removing the additive deposited on the surface is being performed.

This is a rather complicated task. In addition, when forming a coating layer, there is a coating of weather resistant paint, but the above-mentioned problems and stress relaxation occur due to secondary heating during curing, especially in the case of plate-like objects, warpage etc. appear, and defects such as distortion of the perspective image May occur.

[Problems to be Solved by the Invention] The present invention is to solve the above-mentioned problems of the prior art, and can be mass-produced on a factory line without secondary processing of general-purpose products. It is an object of the present invention to provide a method capable of producing a RPVC plate which is suitable and does not have the above-mentioned various disadvantages.

Means for Solving the Problems The present invention contains 30 to 70 mol% of a unit based on a fluoroolefin selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride and hexafluoropropylene, and is crosslinked. Polyvinyl chloride sheet (A) and polyvinyl chloride sheet (B) coated with a paint containing as a main component a fluorinated copolymer having moieties (a) and an acrylic copolymer (b) compatible with (a) A) a method for producing a polyvinyl chloride plate having a layer based on the above coating material and having excellent weather resistance, wherein

As the coating material used in the present invention, a unit based on a fluoroolefin selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride and hexafluoropropylene (hereinafter, simply referred to as fluoroolefin) is 30 to 70 mol%. Fluorine-containing copolymers containing (a) and (a) having a crosslinking site
The main component is an acrylic copolymer (b) that is compatible with the above.

Here, as the fluorinated copolymer (a), a solvent-soluble fluorinated copolymer having a fluorine content of 10% by weight or more based on fluoroolefin units is preferably employed.

The fluorine-containing copolymer (a) has a fluorine content of 10% by weight or more, preferably 10% by weight, based on fluoroolefin units.
~ 70% by weight, more preferably 15 ~ 50% by weight,
Those having an intrinsic viscosity of 0.01 to 4.0 dl / g measured in tetrahydrofuran in an uncured state are used. If the fluorine content is less than 10% by weight, the intended effect of improving weather resistance is reduced. Further, when the intrinsic viscosity is in the above range, the paintability as a coating material is good, and the physical properties of the formed film are also excellent.

As such a fluorinated polymer, a copolymer of a fluoroolefin and an ethylenically unsaturated compound as a comonomer copolymerizable with the fluoroolefin is preferably employed.

Further, as the ethylenically unsaturated compound as a monomer copolymerizable with a fluoroolefin, olefins,
Examples thereof include vinyl ethers, vinyl esters, allyl ethers, allyl esters, and (meth) acryloyl group-containing compounds.

Among them, olefins having excellent copolymerizability with fluoroolefins, vinyl ethers, vinyl esters, allyl ethers having a linear, branched or alicyclic alkyl group having about 1 to 10 carbon atoms. Is preferred.

The fluorinated copolymer (a) contains 30 to 70 mol% of a unit based on a fluoroolefin. If it is less than 30 mol%, the effect of improving weather resistance is not sufficient, and if it is more than 70 mol%, the solubility in a solvent tends to decrease, which may hinder the application work as a paint. In the copolymer, the fluoroolefin and the ethylenically unsaturated compound may be used alone or in combination of two or more.

Since the fluorine-containing copolymer (a), which is a main component of the coating material of the present invention, has a cross-linking site, the copolymers react with each other via other components or a curing agent, or the copolymers directly connect with each other. It reacts to form a three-dimensional network structure, giving a favorable result that the solvent resistance, acid resistance and alkali resistance of the coating are improved.

As the crosslinking site, a hydroxyl group, a carboxylic acid group, an acid amide group, an amino group, an active hydrogen-containing group such as a mercapto group,
Examples include an active halogen atom such as an epoxy group, a carbon-carbon unsaturated group, bromine, and iodine. Of these, active hydrogen-containing groups are preferred in that they have excellent reactivity with isocyanate-based curing agents, aminoplast-based curing agents, and the like, which are usually used as curing agents, and hydroxyl groups are particularly preferred.

Methods for introducing such a cross-linking site into the copolymer include, for example, cross-linking of hydroxyalkyl vinyl ether, hydroxyalkyl allyl ether, hydroxyaryl vinyl ether, hydroxyalkyl allyl ether, glycidyl vinyl ether, (meth) acrylic acid, allyl vinyl ether, diaminoethyl vinyl ether, etc. A method in which a monomer having a reactive site is copolymerized, or a method in which an acid anhydride, an isocyanate, an alkyl (meth) acrylate, or the like is reacted with a fluorinated copolymer to be added, is employed.

Further, as a method of hydrolyzing a part of the copolymer, after copolymerizing a monomer having a hydrolyzable ester group, the copolymer is hydrolyzed to form a carboxylic acid group in the copolymer. Alternatively, a method of generating a hydroxyl group is also employed. Further, a method of introducing a carboxylic acid group by reacting a divalent carboxylic anhydride such as succinic anhydride with the hydroxyl group-containing copolymer is also employed.

The acrylic polymer (b) compatible with the fluorinated copolymer (a), which is a main component of the coating material in the present invention, is a unit based on an alcohol ester of (meth) acrylic acid having 1 to 12 carbon atoms. And an acrylic polymer having a molecular weight of 500 to 80,000 is preferred. Such acrylic copolymers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isobutyl methacrylate, n-butyl (meth) acrylate, tert-butyl (meth) acrylate, and (meth) A polymer having a unit based on a monomer selected from acrylonitrile is exemplified.

Further, preferably, a copolymer of two or more units based on these monomers, or a single monomer such as an acrylate ester, styrene, maleic acid, a vinyl ester (such as vinyl acetate), or a vinyl silane other than those described above. Copolymers having units based on the body are used. More preferably, in the acrylic polymer, a polymer having a cross-linking site is cross-linked by a reaction with a cross-linking site of a fluorine-containing copolymer, and a coating film of a paint has a three-dimensional network structure and exhibits excellent characteristics.

Here, as the crosslinking site in the acrylic polymer (b), a hydroxyl group, a glycidyl group, a carbamoyl group, a silanol group and the like are preferable.

For example, the introduction of a hydroxyl group can be performed using 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate,
-Hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate and the like, and the introduction of a glycidyl group is glycidyl (meth) acrylate,
(Β-methyl) glycidyl (meth) acrylate, etc.
Further, the introduction of a carbamoyl group is performed by (meth) acrylamide, dimethyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-octyl (meth) acrylamide, diacetone (meth) acrylamide, or the like.
The introduction of the silanol group is carried out by copolymerizing a monomer such as vinyl silane with a comonomer that gives the acrylic polymer or copolymer.

The silanol group can also be introduced by a method of adding an isocyanate silane or a silane coupling agent to a hydroxyl group-containing acrylic polymer.

Here, the acrylic polymer (b) may be a mixture of a polymer having a cross-linking site and a polymer having no cross-linking site. It does not include a copolymer with a monomer having a hydroxyl group, a glycidyl group, a carbamoyl group, or the like. The proportion of the acrylic polymer having no cross-linking site is preferably up to 50% by weight based on the acrylic polymer having the cross-linking site.

Further, a curing agent can be added to the main components (a) and (b) of the paint, and the curing agent is compatible with the fluorine-containing copolymer (a) and the acrylic polymer (b). What melts and hardens them is used.

Examples of such curing agents include polyisocyanate-based, for example, hexamethylene diisocyanate, non-yellowing diisocyanates such as isophorone diisocyanate, and adducts thereof, and a block obtained by blocking an isocyanate group with a blocking agent such as phenol. Isocyanate or the like can be employed as a preferable one.

Also, various curing agents such as melamine, metal alkoxide, urea resin, polybasic acid, epoxy, and silanol can be used. Here, the fluorinated copolymer (a)
When the crosslinking site of is a hydroxyl group, a polyisocyanate-based or metal alkoxide-based is preferred. As the melamine-based curing agent, one or two or more of lower alcohols such as methanol, ethanol, propanol and butanol can be used.
Melamine partially etherified by more than one species is preferably employed. Such a curing agent has a very useful effect on the formation of a tertiary network of a copolymer or polymer having a crosslinked site.

For the purpose of accelerating the curing, a catalyst may be used in combination with the curing agent.Examples of such a curing aid include dibutyltin dilaurate as an isocyanate curing agent, and a paratoluenesulfonic acid-based catalyst as a melamine curing agent. It is used in an amount of 0.001 to 2 parts by weight based on 100 parts by weight of the fluorinated copolymer (a).

The respective proportions of the main constituent components in the paint of the present invention are preferably from 30 to 90% by weight of the fluorinated copolymer (a) and from 10 to 70% by weight of the acrylic polymer (b). When the amount of the fluorinated copolymer (a) is small, the fluorine content is reduced, and the intended effect of improving the weather resistance is not achieved. On the other hand, when the amount of the acryl-based polymer (b) is small, the adhesion to the substrate is low. Decrease.

Each of the fluorine-containing copolymer (a) and the acrylic polymer (b) is not limited to one type within the above-mentioned ratio, and two or more types may be used in combination.

The curing agent is used at a ratio of 0 to 20% by weight based on the total amount of the fluorine-containing copolymer (a) and the acrylic polymer (b).

In the coating material, in addition to the main constituent components, the amount of the fluoropolymer (a) and the acrylic polymer (b) was set at 0.
The weather resistance can be further improved by including 5 to 3% by weight of the ultraviolet absorber. As such ultraviolet absorbers, conventionally known or well-known 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone,
2-hydroxy-4-n-octyloxybenzophenone, 2-hydroxy-4- (1-methyl-2-hydroxyethoxy) benzophenone, 2-hydroxy-4-
Benzophenones such as (2-hydroxy-3-methacryloxypropoxy) benzophenone or 2- (2 ′
-Hydroxy-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-
A benzotriazole-based compound such as (butylphenyl) benzotriazole is used alone or in combination.

Further, an acrylic polymer (c) having a fluoroalkyl group may be added to such a paint to improve the water repellency of the plastic sheet. When the acrylic polymer (c) having such a fluoroalkyl group has a crosslinking site similar to that of the fluorinated copolymer (a) or the acrylic polymer (b),
It is preferable because water repellency and the like are maintained for a long time.
The addition amount of the acrylic polymer (c) having such a fluoroalkyl group is from 0.1 to 100 parts by weight in total per 100 parts by weight of the fluorinated copolymer (a) and the acrylic polymer (b).
It is preferable to employ it in the range of about 30 parts by weight.

In addition, for the purpose of improving the properties, paints include, for example, an antifoaming agent, an antistatic agent, a pigment, a dispersion stabilizer, a viscosity modifier,
Additives such as a leveling agent and an anti-gelling agent may be added. The compounding of the pigment has the effect of shading the coating.

The coating material of the present invention is a fluorine-containing copolymer (a) as described above.
And a main component such as an acrylic polymer (b), and, if necessary, a curing agent, an ultraviolet absorber, an acrylic polymer having a fluoroalkyl group (c), and other additives dissolved in an organic solvent. However, as the solvent used, for example, aromatic hydrocarbons such as toluene and xylene, alcohols such as propanol and butanol, ethyl acetate and esters such as butyl acetate,
Various general organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone, glycol ethers such as ethyl cellosolve, and various commercially available thinners. A coating composition having a concentration of 1 to 60% by weight, preferably 5 to 50% by weight, is suitable in terms of workability for forming a film.

In preparing the paint, for example, ball mill, paint shaker, sand mill, jet mill, three rolls,
It is carried out by using various devices used for ordinary coating, such as a kneader, and is not particularly limited. At this time, additives such as those described above can be added.

In the present invention, the polyvinyl chloride may be polyvinyl chloride alone, or may be a mixture of ordinary polyvinyl chloride additives. Examples of the additive include a stabilizer, a plasticizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, an impact resistance improver, and a reinforcing agent.

In addition, the polyvinyl chloride sheet (A) has a thickness of 0.
Those having a size of about 1 to 0.5 mm are preferably employed. A thin film is not preferable because the workability at the time of lamination with the polyvinyl chloride sheet (B) is poor, and the RPVC film itself may shrink when the paint is dried. Also, a thick one is not preferable because it is difficult to wind it into a roll shape and it is not suitable for mass production. In particular, those having a thickness of 0.1 to 0.3 mm are preferably employed. Further, the polyvinyl chloride sheet (A) preferably has a smooth surface on at least one side. When applying the above-mentioned paint, if it is applied to a smooth surface, a coating film having a uniform film thickness can be easily obtained.

Furthermore, the method of applying the above-mentioned paint to the polyvinyl chloride sheet (A) is not particularly limited, and any of the usual paint coating methods may be employed. Further, it is preferable that the paint is applied so that the dry film thickness is about 10 to 50 μm. If the film thickness is too small, uneven coating and repelling may occur, and this is not preferable because it causes a decrease in weather resistance. Further, it is difficult to form a thick coating film, and it is not economically preferable.

Further, when applying the above-mentioned paint, it is sufficient that the paint is dried to such an extent that tack is eliminated, that is, to the touch dryness.
The paint can be cured by heating when the polyvinyl chloride sheet (A) and the polyvinyl chloride sheet (B) are subsequently heated and pressed, so that it is not necessary to cure the paint when applying to the polyvinyl chloride sheet (A). Insufficient drying may cause blocking during storage of the polyvinyl chloride sheet (A), which is not preferable. Usually, a drying time of about 30 seconds to 10 minutes at a drying temperature of about 50 to 70 ° C. is employed.

The thickness of the polyvinyl chloride sheet (B) is not particularly limited, but usually a sheet having a thickness of about 0.3 to 0.8 mm is used. Further, the polyvinyl chloride sheet (B) preferably has an uneven surface. When a sheet having a smooth surface is used, it is not preferable because air bubbles interposed between the sheets cannot be completely removed at the time of thermocompression bonding, and air bubbles remain in the product. Such a polyvinyl chloride sheet (B) can be manufactured by a calender roll or the like. Further, the state of the unevenness can be adjusted by adjusting the rotation ratio of the calendar roll.

In addition, when heating and pressing the polyvinyl chloride sheets (A) and (B), a plurality of polyvinyl chloride sheets (B) may be stacked in order to obtain a polyvinyl chloride plate having a desired thickness. In addition, in order to obtain a polyvinyl chloride plate having a weather-resistant coating layer on both sides, a polyvinyl chloride sheet (A) may be disposed above and below as in (A) / (B) / (A).
The lamination of (A) and (B) is performed by arranging such that the unpainted surface of (A) is in contact with (B).

The thermocompression bonding can be performed using a press device or the like. For example, a polyvinyl chloride sheet may be interposed between mirror-finished metal plates, and heated and pressed. The conditions of the heat and pressure bonding are a temperature of about 130 to 170 ° C, 20 to 60 kg / cm ²
It is preferable to carry out at a pressure of about 10 minutes or more. If the temperature or the pressure is low, heat fusion of the polyvinyl chloride sheet may not be sufficiently achieved, which is not preferable. If the temperature is low or for a short period of time, the above-mentioned coating composition may be insufficiently cured, and the weather resistance and the solvent resistance may not be sufficiently exhibited.

During this thermocompression bonding, the polyvinyl chloride sheet is heat-sealed and an integrated polyvinyl chloride plate is obtained.However, the heat-sealing action also works between the paint and the polyvinyl chloride sheet, which is compared to normal coating. Excellent adhesion is obtained.

The thickness of the polyvinyl chloride plate obtained by the method of the present invention can be appropriately selected as desired, but is preferably in the range of about 1 to 10 mm for the purpose of use as a structural material. . If the material is too thin, sufficient strength as a structural material cannot be obtained, and if it is too thick, transparency may decrease, which is not preferable.

[Examples] Examples, Comparative Examples As coatings, chlorotrifluoroethylene, cyclohexyl vinyl ether, ethyl vinyl ether and hydroxybutyl vinyl ether were copolymerized at 55, 12, 15 and 18% by weight, respectively, 100 parts by weight of a fluorinated copolymer, Methyl methacrylate, isobutyl methacrylate and hydroxyethyl methacrylate are each 25,
Acrylic copolymer 100 copolymerized at 60 and 15% by weight
Parts by weight, 500 parts by weight of a solvent (methyl ethyl ketone), 67 parts by weight of a block isocyanate-based curing agent (manufactured by Nippon Polyurethane, trade name: Coronate C-2507), and 20 parts by weight of an ultraviolet absorber (manufactured by Kyodo Chemical, trade name: Biosoap 130) Was used.

Manufacture of polyvinyl chloride sheet A 100 parts by weight of polyvinyl chloride, 2 parts by weight of zinc stearate, 0.5 parts by weight of lead stearate, 0.5 parts by weight of dibutyltin diaurate, 2 parts by weight of monobutyltin tri (methyl malate), 0.5 parts by weight of epoxidized soybean oil Parts by weight, and the thickness of the surface is smoothed using a calender roll.
A 0.2 mm polyvinyl chloride sheet was obtained. The above coating material was applied to a dry film thickness of 20 μm using a reverse coater, and then air-dried at 60 ° C. for 3 minutes to obtain a polyvinyl chloride sheet A.

As the polyvinyl chloride sheet B, a sheet having the same composition as that of the above-mentioned polyvinyl chloride sheet A and having a thickness of 0.5 mm with irregularities produced by using a calender roll was used.

^Two polyvinyl chloride sheets A and six polyvinyl chloride sheets B were laminated between the mirror-finished aluminum plates and pressed at 160 ° C. and 30 kg / cm ² for 10 minutes. Thereafter, the resultant was gradually cooled to obtain a polyvinyl chloride plate (thickness: about 3 mm) having a layer based on the above-mentioned paint on the surface.

As a comparative example, a polyvinyl chloride plate obtained in the same manner except that no paint was applied was used.

Tensile strength, elongation, falling ball impact, Charpy impact, light transmittance, and haze of each polyvinyl chloride plate before and after the weather resistance promotion test (exposure to a sunshine carbon arc type weather meter for 2000 hours) were measured. It is shown in the table.

[Effects of the Invention] According to the method of the present invention, it is possible to produce a polyvinyl chloride plate having excellent weather resistance, good light transmittance, and free from image distortion and the like. In addition, since there is not much difference from the process of manufacturing a normal polyvinyl chloride plate, mass production in a factory is possible. Furthermore, the method of the present invention does not require a heat treatment step after the manufacture of the plate, and thus eliminates problems such as warpage of the plate.

Claims (1)

(57) [Claims] 1. A fluorine-containing copolymer containing 30 to 70 mol% of a unit based on a fluoroolefin selected from the group consisting of tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride and hexafluoropropylene and having a crosslinked site. (A) and heat-compression bonding of a polyvinyl chloride sheet (A) and a polyvinyl chloride sheet (B) coated with a paint mainly containing an acrylic copolymer (b) compatible with (a). A method for producing a polyvinyl chloride plate excellent in weather resistance having a layer based on the above coating material on the surface.