JPH0820697A - Vinyl chloride-based plastisol composition - Google Patents

Abstract

PURPOSE:To prevent cracking, blister, etc., from occurring due to moisture absorbed in a film by allowing the film to stand at high temperatures and high humidities during the thermal baking. to stand at high temperatures and high humidities. CONSTITUTION:This composition is obtained by blending a water absorbent comprising calcium oxide in a vinyl chloride-based plastisol composition such as a sealing composition consisting essentially of a vinyl chloride-based resin and a plasticizer and adding a mercapto-based silane coupling agent thereto. Hygroscopic cracking and blistering properties of a film, especially in coating thereof and then allowing the formed film to stand in its intact state can be prevented during the thermal baking of the film by adding the coupling agent thereto. The hygroscopic cracking and blistering properties in preheating the film and allowing the preheated film to stand and carrying out the intermediate coating and subsequently allowing the film to stand can be prevented by blending a relatively large amount of the calcium oxide therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl chloride-based plastisol composition used as a sealing composition for automobile bodies, an undercoat composition, a chipping resistant coating composition and the like.

[0002]

2. Description of the Related Art The body of an automobile is assembled by welding steel plates together by welding or by using an adhesive or the like.
A sealing composition and an undercoat composition are applied for the purpose of airtightness, dustproofing, rustproofing, and the like. Further, a coating composition for chipping resistance is applied to the lower floor of a vehicle body, a wheel house, etc. for the purpose of chipping resistance, rust prevention, and the like.

[0003] Conventionally, these sealing compositions and the like are excellent in rust-preventive property, can satisfactorily fill gaps between steel plate joints, and can form a relatively thick coating film. Thus, vinyl chloride-based plastisol compositions are commonly used. This plastisol composition contains a vinyl chloride resin composed of a vinyl chloride homopolymer, or a copolymer with vinyl acetate or the like as a main component, and a plasticizer,
A filler, other additives and the like are added to this. Examples of such vinyl chloride-based plastisol compositions are disclosed in, for example, Japanese Patent Publication No. 59-52901, Japanese Patent Publication No. 59-78279, Japanese Patent Publication No. 63-6103, and Japanese Patent Publication No. 1-251515. Mention may be made of those mentioned, which are mainly concerned with additives for increasing the adhesion.

However, such a vinyl chloride-based plastisol composition is made of a material that easily absorbs moisture, and therefore the plastisol composition is used in a vehicle body or the like under high temperature and high humidity conditions such as the rainy season and summer. If the coating film is left for a long time after coating, cracks and swelling may occur during heating and baking of the coating film. This occurs because the moisture absorbed in the coating film while standing is suddenly released as bubbles by the heat of baking, or the bubbles are not discharged from the coating film and harden as it is. is there.

Such cracking and swelling of the coating film not only gives a bad appearance, but also significantly deteriorates the rust preventive property and the sealing property. Further, if such cracks, swelling, etc. occur after the intermediate coating or the top coating, even those coatings will be damaged.

Therefore, in order to prevent cracking and swelling of the coating film of the vinyl chloride plastisol composition due to such moisture absorption, it is known to incorporate a water absorbing agent such as calcium oxide into the composition. An example of this is described in JP-A-6-16891 proposed by the present applicant, in which calcium oxide is blended in a vinyl chloride-based plastisol composition, and this calcium oxide is also used. It teaches that powder having an average particle size of 2 μm or less, which has a high reaction rate with water, is preferable.

[0007]

As described above, by adding calcium oxide to the vinyl chloride plastisol composition, calcium oxide reacts with water to be converted into calcium hydroxide, so that the absorbed moisture is oxidized. Can be absorbed by calcium. Therefore, even if the coating film of the plastisol composition is left under high temperature and high humidity and absorbs water, it is possible to prevent the coating film from cracking, swelling or the like during heating and baking.

By the way, a coating film of a plastisol composition applied as a sealing composition for an automobile body is once bake-cured by preheating, but again in the subsequent coating process of the vehicle body during intermediate coating and top coating. It will be heated and baked. Therefore, considering that the coating film of the plastisol composition is left under high temperature and high humidity after preheating or intermediate coating, it is necessary to add a relatively large amount of calcium oxide. Further, since the coating film in the sol state is more likely to absorb moisture than the cured coating film, it is necessary to similarly add a relatively large amount of calcium oxide even when a long standing period is planned.

However, when a relatively large amount of calcium oxide as a water absorbing agent is blended in this way, the cracking and swelling properties due to moisture absorption of the coating film after preheating and after intermediate coating are improved in proportion to the amount added. When the coated plastisol composition was left in the sol state as it was, the moisture absorption cracking and swelling properties of the sol were not improved so much, but in some cases were rather lowered.

Therefore, an object of the present invention is to provide a vinyl chloride plastisol composition having improved moisture absorption cracking and swelling properties when left in a sol.

[0011]

The present inventor has found and confirmed that the moisture absorption cracking and swelling properties of the sol when left standing are remarkably improved by the addition of the mercapto silane coupling agent.

That is, the vinyl chloride-based plastisol composition according to the present invention contains a vinyl chloride-based resin and a plasticizer, a water absorbing agent composed of calcium oxide, and a mercapto-based silane coupling agent as essential components.

Here, examples of the mercapto silane coupling agent include mono-, di-, and trimercaptosilane, and trimercaptosilane is particularly preferable. Then, as typical representative examples thereof, trimethylmercaptosilane, triethylmercaptosilane, tripropylmercaptosilane and the like can be mentioned. The mercapto-based silane coupling agent may be added to the vinyl chloride-based plastisol composition in a small amount, and is generally 0.2 to 3.0% by weight, preferably 0.5 to 1% by weight, based on the entire composition. It can be added in a proportion of 0.5% by weight. If it is less than 0.2% by weight, a sufficient practical effect cannot be generally obtained, and if it is too large, the practical effect is saturated, which is uneconomical.

Calcium oxide as an absorbent is
The plastisol composition may be blended in an appropriate ratio depending on the temperature and humidity conditions under which the coating film is left and the period. However, if too much is added, the appearance of the coating film will deteriorate,
Further, when the coating film is further coated, it may adversely affect the coating film. Therefore, the content of calcium oxide is generally preferably 13% by weight or less, and more preferably 11% by weight or less, based on the entire composition. However, this is not a limitation, and a larger amount than this is also possible. Also,
In general, it is preferable to add 1.5% by weight or more of calcium oxide, but when the standing period after preheating of the coating film of the plastisol composition or after intermediate coating is, for example, 4 days, the mixing ratio is 7% by weight or more. Preferably there is.

The other components of the vinyl chloride-based plastisol composition according to the present invention are the same as conventional ones.

The vinyl chloride resin is a homopolymer or a copolymer of vinyl chloride, that is, a copolymer of vinyl chloride and other vinyl monomers. In the present invention, any of them is used alone. Alternatively, they can be mixed and used.

The vinyl-based monomer copolymerized with vinyl chloride is vinyl acetate, vinyl propionate,
Vinyl stearate and other vinyl esters, vinyl methyl ether, vinyl isobutyl ether and other vinyl ethers, diethyl maleate and other maleic acid esters, dibutyl fumarate and other fumaric acid esters, methyl acrylate, 2-hydroxyethyl acrylate,
Examples thereof include acrylic acid esters such as 2-ethylhexyl acrylate or similar methacrylic acid esters, acrylonitrile, vinylidene chloride and the like. They are,
Any one kind or two or more kinds thereof can be used, but it is generally copolymerized with vinyl chloride in a proportion of 30% by weight or less, preferably 20% by weight or less. However, among these, vinyl acetate is the most common monomer to be copolymerized with vinyl chloride, and is also preferable for adhesiveness.

As the vinyl chloride resin, its paste resin can be generally used, but it is also possible to use a blending resin or other resin in combination therewith. The specific composition or blending thereof can be appropriately determined according to the application, etc., but when the paste resin and the blending resin are mixed and used, the ratio is 3/1 to 1/3 by weight. Are generally preferred.

As the plasticizer, any of those generally used for forming plastisols of vinyl chloride resins can be used. Examples of such a plasticizer include dioctyl phthalate (DOP), di-2-ethylhexyl phthalate, and diisononyl phthalate (DI
NP) and other phthalate esters, di-2-ethylhexyl adipate (DOA), trioctyl trinolitate (TOTN), sebacate esters, azelaate esters and other aromatic and aliphatic di- and tricarboxylic acid esters, and phosphoric acid Examples thereof include phosphates such as triphenyl and tricresyl phosphate, epoxy-based plasticizers such as epoxidized soybean oil, and the like. These plasticizers can be appropriately selected and used according to the desired physical properties such as viscosity and curability of plastisol, and generally range from 30 to 300 parts by weight per 100 parts by weight of vinyl chloride resin. Can be compounded.

A part of the plasticizer can be changed to an organic solvent or the like. Then, as such a solvent, an aromatic solvent or the like, preferably a solvent having a boiling point as high as that of the plasticizer, is used.

Further, in the vinyl chloride plastisol composition of the present invention, a filler, an adhesiveness-imparting agent, an anti-sagging agent, a pigment, and other additives are appropriately blended or added to the vinyl chloride plastisol composition of the present invention. You can

Examples of the filler include calcium carbonate, magnesium carbonate, carbonates and sulfates of alkaline earth metals such as barium sulfate, mica, silica, talc, diatomaceous earth, kaolin and the like, which are used alone. , Or can be used in combination as appropriate. In addition, organic fillers such as cellulose powder and powder rubber can also be used if necessary.

The adhesiveness-imparting agent is for increasing the adhesiveness of the coating film to the article to be coated, and any one of acrylic, polyamide, epoxy, blocked isocyanate and the like may be used alone or in combination. Can be used. Among these, polyamide-based or block isocyanate-based adhesion promoters such as block urethane prepolymers and block isocyanurates are particularly preferable.

The anti-sagging agent is used for adjusting the viscosity of the composition while keeping balance with other components, and ultrafine calcium carbonate, fine silica and the like are preferably used also as a filler. be able to. Further, as the pigment, any pigment can be used, but a color pigment that also serves as an extender pigment such as titanium oxide or carbon black can be particularly preferably used. Further, other additives include metal soaps, inorganic acid salts, plastisol stabilizers such as organometallic compounds, thickeners such as organic bentonite, and the like, and these may be used as necessary. it can.

The vinyl chloride-based plastisol composition of the present invention as described above can be applied in an arbitrary thickness and form using, for example, a discharge gun or a spray gun. Then, the baking and curing of the applied plastisol composition is generally 120-120 in the case of a sealing composition.
It can be performed by preheating at a temperature of 160 ° C.

[0026]

In the present invention, since the mercapto-based silane coupling agent is added to the vinyl chloride-based plastisol composition containing the water absorbing agent composed of calcium oxide, the applied plastisol composition is in a sol state at high temperature and high temperature. Improves hygroscopic cracking and swelling when left in a sol that has been left in a humid environment. The reason for this is not clear, but the water absorption of calcium oxide is increased by the mercapto-based silane coupling agent, and the evaporation of water in the coating film during baking to the outside is facilitated without bubbles. It is thought that this is because it becomes.

[0027]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

The vinyl chloride plastisol composition of the present invention was embodied as a sealing composition for automobile bodies, and the composition (% by weight) shown in FIG.
A plastisol composition was prepared.

<Compounding> As shown in FIG.
Through the sealing plastisol composition of Example 5, a vinyl chloride resin, a plasticizer, an adhesiveness-imparting agent, an anti-sagging agent,
In addition to the filler and calcium oxide which is a water absorbing agent,
Further, a mercapto silane coupling agent is added. In these examples, the mixing ratios of the filler and the components other than calcium oxide are the same, the mixing ratio of calcium oxide is variously changed, and the mixing ratio of the filler is increased or decreased accordingly.

Here, the vinyl chloride resin is a paste resin (39) made of a copolymer of vinyl chloride and vinyl acetate.
J Nippon Zeon Co., Ltd.), and was blended in 23% by weight in each example.

As the plasticizer, diisononyl phthalate (D
INP) is used, and the compounding ratio thereof is 22% by weight.
The adhesiveness-imparting agent is a block isocyanate-based adhesiveness-imparting agent (Adesta # 751 manufactured by Mitsubishi Kasei Vinyl Co., Ltd.), and the compounding ratio thereof is 5% by weight. As the anti-sagging agent, colloidal calcium carbonate (Neolite SP manufactured by Takehara Chemical Industry Co., Ltd.) was used, and was mixed at 18% by weight.

Heavy calcium carbonate (NS-100 manufactured by Nitto Koki Co., Ltd.) was used as the filler, and the total amount of calcium carbonate (CML # 31) as the water absorbing agent was 2
5% by weight is blended. The blending amount of calcium oxide was 5% by weight in Example 1, 7% by weight in Example 2, 9% by weight in Example 3, and 11% by weight in Example 4.
In Example 5, it is 13% by weight.

The other compounded components are a high-boiling solvent, titanium dioxide, and a stabilizer, which are contained in a total amount of 6% by weight.

In addition to these formulations, 1% by weight of a mercapto-based silane coupling agent (A-189, Nippon Unicar Co., Ltd.) consisting of triethylmercaptosilane was added to each example.

The plastisol compositions of Examples 1 to 5 were prepared by uniformly mixing the materials by using a planetary mixer and then vacuum defoaming and stirring for 60 minutes.

Further, for comparison with these examples,
The plastisol composition of Comparative Example 1 was prepared in the same manner as in the example. The plastisol composition of Comparative Example 1 has the same composition as in Example 3 except that the mercapto-based silane coupling agent is not added. However, the composition of the filler is 1
Weight% increased to 17% by weight.

<Evaluation Test> Examples 1 to 5 described above
Further, the sealing plastisol composition of Comparative Example 1 was subjected to an evaluation test of moisture absorption cracking / swelling property during baking of the coating film. In addition to this, the appearance of the coating film was also evaluated.

The evaluation test of moisture absorption cracking / swelling property is a test in which the plastisol composition is applied and then left as it is under high temperature and high humidity (solation), and the plastisol composition is applied and then preheated once. A test of baking and curing, and then leaving it under high temperature and high humidity (left after preheating),
After applying the plastisol composition, it was once preheated to be baked and cured, and then an intermediate coating material was applied, baked and dried, and then allowed to stand under high temperature and high humidity (left after intermediate coating). Each test was specifically performed as follows according to the actual painting process of the car body.

[Leaving sol] The plastisol composition was applied to a test plate in a shape of 1 mm thickness, 10 mm width × 100 mm length, and left as it was under a temperature and humidity condition of 30 ° C. × 80% RH for 96 hours (4 days). . Then, the coating film was preheated at 120 ° C. for 10 minutes to be baked and cured, and cracks and swelling of the coating film at that time were observed and evaluated.

[Lefting after preheating] Similarly to the above, the plastisol composition was applied to a test plate in a thickness of 1 mm, and immediately after that, preheating was performed at 120 ° C. for 10 minutes to bake and cure the coating film. It was left for 96 hours (4 days) under the same conditions of 30 ° C. and 80% RH. And this one
Baking was again performed under heating conditions of 40 ° C. for 30 minutes, and cracks and swelling of the coating film at that time were observed and evaluated.

[Left after intermediate coating] In the same manner as above, the plastisol composition was applied to a test plate in a thickness of 1 mm, and immediately at 120 ° C.
After pre-heating for 10 minutes for 10 minutes to cure the coating film by baking, an amino / polyester-based intermediate coating material was overlaid (dry film thickness: 20 μm) and baked and dried under heating conditions of 140 ° C. for 30 minutes. Then, this was left for 96 hours (4 days) under a temperature and humidity condition of 30 ° C. × 80% RH. Next, after water-polishing the coating film of the intermediate coating, it is again baked and dried under the heating condition of 165 ° C. for 15 minutes which is a general baking condition of the top coating, and the cracks and swelling of the coating film at that time are observed. And evaluated.

The criteria for evaluation of moisture absorption cracking and swelling are as follows. ◯: No abnormalities (no occurrence of cracks, swelling, etc.) Δ: Occurrence of slight cracks, swelling, etc. ×: Occurrence of cracks, swelling, etc. For the evaluation of the appearance of the coating film, see “Sol” above. The coating film which had been baked and cured by preheating in "standing" was observed and evaluated according to the following criteria. ◯: No roughness on the surface x: Roughness on the surface The results of these evaluation tests are also shown in FIG.

<Results of Evaluation Test> As shown in FIG. 1, the plastisol compositions of Examples 1 to 5 to which a mercapto-based silane coupling agent was added, the coating film was left as it was in a sol state under hot and humid conditions. If left in a sol, moisture absorption cracks
Good results were obtained in all of the blistering properties. On the other hand, in the plastisol composition of Comparative Example 1 to which the mercapto-based silane coupling agent was not added, the hygroscopic cracking / swelling property was poor when the sol was left, and the coating film after moisture absorption during preheating had cracks, swelling, etc. Occurred.

From this result, in particular, from the comparison between Example 3 and Comparative Example 1 which have substantially the same composition except for the presence or absence of the addition of the mercapto silane coupling agent, the mercapto silane coupling agent was selected. It can be seen that the addition can improve the hygroscopic cracking and swelling properties of the plastisol composition when it is left in the sol.

Further, in this evaluation test result, the mixing ratio of calcium oxide was 5% by weight, which was relatively small in Example 1.
Shows that moisture absorption cracking and swelling tend to be insufficient when left after preheating and left after intermediate coating. On the contrary,
In Example 5 in which the blending ratio of calcium oxide was relatively large and 13% by weight, the appearance of the coating film tended to deteriorate. Therefore, the mixing ratio of calcium oxide is preferably 7% by weight or more when the coating film of the plastisol composition may be left under high temperature and high humidity for a long time after preheating or intermediate coating. Further, when a good appearance is required for the coating film of the plastisol composition, 11
It can be seen that it is preferably not more than wt%.

Thus, an example in which the vinyl chloride-based plastisol composition of the present invention was embodied as a sealing composition for automobile bodies has been described. However, the present invention is not limited to this example. Instead, the type and blending ratio of the components such as vinyl chloride resin and plasticizer can be variously changed. Further, it can be suitably applied not only as a sealing composition, but also as an undercoat composition, a chipping-resistant coating composition, or the like. Furthermore, these plastisol compositions can be advantageously applied not only to automobile bodies, but also to vehicles other than automobiles such as railways, home electric appliances, and the like.

[0047]

As described above, the vinyl chloride plastisol composition according to the present invention comprises a vinyl chloride resin and a plasticizer, a water absorbing agent composed of calcium oxide, and a mercapto silane coupling agent as essential components. To do.

Therefore, since the mercapto-based silane coupling agent is added in addition to calcium oxide which is a water absorbing agent, the applied plastisol composition is left as it is in a sol state under high temperature and high humidity, and then baked by heating. In this case, moisture absorption cracking and swelling can be improved. Therefore, even in the case where the standing period is long, it is possible to prevent the occurrence of cracking, swelling, etc. during heating and baking due to moisture absorption. And, by adding a relatively large amount of calcium oxide, not only when the sol is left as it is, but also when it is left under high temperature and high humidity after preheating and after intermediate coating and then baked under heat, the moisture absorption cracking and swelling properties are also improved. can do.

[Brief description of drawings]

FIG. 1 is a table showing the blending (wt%) of vinyl chloride plastisol compositions for sealing and the results of evaluation tests of Examples and Comparative Examples of the present invention.

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Claims (1)

[Claims] 1. A vinyl chloride plastisol composition comprising a vinyl chloride resin and a plasticizer, a water absorbing agent made of calcium oxide, and a mercapto silane coupling agent as essential components.