JPH111658A - Undercoat composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an undercoat compsn. which can form a uniformly foamed cell layer having a uniform surface skin and exhibiting enhanced impact absorption and soundproofness by using a polyvinyl chloride resin, a plasticizer, a calcium carbonate powder, a blowing agent, a blowing assistant, and a moisture absorbent as the essential ingredients and using urea or a urea compd. treated with a fatty acid as the blowing assistant. SOLUTION: A vinyl chloride-vinyl acetate copolymer. having a degree of polymn. of 1,500-2,100 and suitably having a vinyl acetate content of 4.0-10.0%, is used as the polyvinyl chloride resin. A combination of a phthalic ester plasticizer [e.g. di-n-butyl phthalate or di-2-ethylhexyl phthalate (DOP)] with at least one plasticizer selected from among polyester-, sulfonate-, and phosphate-based ones is used in an amt. of 35-60 wt.%. The average particle size of calcium carbonate used is pref. 0.03-0.07 μm. Both inorg. blowing agents (e.g. sodium bicarbonate) and org. blowing agents (e.g. azodicarbonamide) can be used. Urea. etc., coated with stearic acid, etc., is used as the blowing assistant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl chloride plastisol-based undercoat having an enhanced shock absorbing capacity and a soundproofing function in order to reduce the noise caused by stones, sand, etc., which are rolled up from tires while the vehicle is running. Hereinafter, it may be referred to as a PVC sol-based undercoat.)

[0002]

2. Description of the Related Art In recent years, the pursuit of comfort, which is one of the needs for automobiles, has been increasing in recent years. 2. Description of the Related Art Conventionally, a PVC undercoat applied to the floor behind a vehicle, a wheel house portion, and a locker portion has been used for the purpose of protecting a vehicle body from damage caused by stepping stones.

[0003] The PVC undercoat has excellent chipping resistance and has an effect of absorbing the impact sound generated by the impact from the stepping stone. However, in order to further improve the impact sound absorbing effect of the PVC undercoat, the coating film thickness of the PVC undercoat had to be increased.

[0004] The effect of reducing the impact sound caused by a stepping stone increases as the film thickness of the PVC undercoat increases. For this reason, conventionally, as a measure to reduce the impact sound caused by stepping stones, the applied film thickness of the non-foamed undercoat has been increased,
Problems such as an increase in the weight of the vehicle body and an increase in cost remain.

[0005]

The inventors of the present invention have tried to add a foaming agent to a PVC sol-based undercoat as a technique for reducing the coating film thickness and increasing the thickness after heat curing. Was found to be improved, and was separately proposed.

When the foamed PVC sol-based undercoat is applied and left as it is for 2 to 3 days, or when baked in a sealer drying furnace and then left for 2 to 3 days, the intermediate coating drying furnace is used thereafter. There is a problem that blisters are generated when printing. This problem was particularly noticeable in summer.

[0007] This is because urea or a urea compound used as a foaming aid is dissolved by being humidified by the moisture present in the vissol-based undercoat and acts unevenly. May be generated, or an uneven foam layer may be formed.

The inventors of the present invention have attempted to treat (coat) urea or a urea compound used as a foaming aid with a fatty acid, and have found that blistering is eliminated, thus completing the present invention. Things.

According to the present invention, a uniform foam cell layer and a surface coating layer are formed under heating effect conditions by increasing the shock absorbing power and imparting a soundproofing function, and the chipping resistance is not increased without increasing the coating weight. Rust resistance and soundproofing performance, in particular, reduce noise caused by stones, sand, etc. rolled up from tires while driving a car, and also prevent the occurrence of blisters during burning. It is an object of the present invention to provide a vinyl chloride sol-based undercoat composition.

[0010]

In order to solve the above-mentioned problems, a vinyl chloride plastisol-based undercoat composition of the present invention comprises a vinyl chloride resin, a plasticizer, a calcium carbonate powder, a foaming agent, and a foaming aid. It is characterized by containing an agent and a moisture absorbent as essential components.

As the polyvinyl chloride resin used in the vinyl chloride plastisol-based undercoat composition of the present invention, a vinyl chloride-vinyl acetate copolymer is used, and its polymerization degree is preferably from 1500 to 2100.
~ 2000 is more preferred. If the degree of polymerization exceeds 2100, the heat-curing properties deteriorate, and sufficient foaming cannot be obtained.

Further, the strength of the coating film is insufficient and the chipping resistance is poor. If the degree of polymerization is less than 1500, the storage stability is poor, and a problem arises in workability in an actual line.

The content of the vinyl acetate resin is 4.0 to 1
0.0% is preferred, and 7.0-9.0% is more preferred. If the content exceeds 10.0%, the change with time in viscosity becomes large and the workability is impaired. If the content is less than 4.0%, the heat-curing properties are poor, foaming is suppressed, and the chipping resistance is poor.

One or more plasticizers selected from phthalic acid-based, polyester-based, sulfonic-acid-based, or phosphoric-acid-based plasticizers are used as the plasticizer used to soften the cured film of the PVC undercoat. Is preferred. Of these plasticizers, phthalic acid-based plasticizers affect the melt viscosity of vinyl chloride resin when heated, improve the balance with the decomposability of the foaming agent, and are effective in forming foam cells of the cured film. Particularly preferred.

As a plasticizer, di-n-butyl phthalate,
Phthalate plasticizers such as di-2-ethylhexyl phthalate (DOP), di-n-octyl phthalate (n-DOP), diisodecyl phthalate (DIDP), and diisononyl phthalate (DINP) are preferably used. However, polyester plasticizers, sulfonic acid ester plasticizers, phosphate ester plasticizers and the like can be used alone or in combination of two or more.

The amount of the plasticizer to be added can be widely used for a paste for a vinyl chloride resin sol.
0% by weight is preferred. If the addition amount is too small, a uniform cured film cannot be obtained even by heating and melting, and a foaming factor with a sufficient expansion ratio cannot be obtained. On the other hand, if the addition amount is too large, the physical properties of the cured film deteriorate, and if the cured film is left, bleed-out of the plasticizer easily occurs on the surface.

In a conventional vinyl chloride plastisol-based chip-resistant coating composition, the average particle size of calcium carbonate added as a filler is 0.08 to 20 μm. In contrast, in the undercoat composition of the present invention,
It is preferable that calcium carbonate added as a kind of filler has an average particle size in a range of 0.03 to 0.07 μm. By making the average particle size of calcium carbonate finer than before, it is possible to effectively prevent the heat sagging resistance from lowering.

It is considered that this is because the thixotropic property of the coating composition was improved and the viscosity of the coating composition was increased by reducing the average particle size of calcium carbonate. If the average particle size of the calcium carbonate is larger than 0.07 μm, the effect of preventing the sagging of the heat sagging by the improvement of the thixotropy cannot be sufficiently obtained.

On the other hand, the average particle size of calcium carbonate is 0.0
When it is smaller than 3 μm, the specific surface area increases and the cohesive force between the calcium carbonate particles increases, so that the secondary and tertiary particles of calcium carbonate are hard to break (blocking phenomenon), and the dispersibility decreases. The effect of preventing reduction in heat sagging due to the improvement in thixotropy cannot be sufficiently obtained, and spray workability also decreases.

The foaming agent generates N ₂ gas or carbon dioxide gas when heated and forms closed cells in the PVC undercoat to increase the volume. Decomposition of the foaming agent is promoted by further adding a foaming aid to the foaming agent, which has the effect of lowering the curing temperature conditions for the PVC undercoat.

Examples of the blowing agent include inorganic blowing agents such as sodium bicarbonate and ammonium carbonate, azodicarbonamide (ADCA), azobisisobutyronitrile (AIB).
N), organic foaming agents such as 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH), unfoamed microballoons and the like can be used.

As the foaming aid of the organic foaming agent, urea and urea-based compounds obtained by treating with a fatty acid are used. The fatty acid treatment may be a coating treatment with stearic acid, palmitic acid, or the like. It is sufficient that the amount of fatty acid to be coated is 3 to 10% by weight based on urea or a urea compound. These ureas or urea compounds can be used alone or in combination. The addition of the foaming aid lowers the foaming start temperature, so that a certain foaming rate can be obtained even under a wide range of baking conditions. This foaming aid can be used in an amount of about 0.2 to 10% based on the PVC undercoat composition.

As the moisture absorbent, calcium oxide is used in an amount of 3 to 2
About 0% by weight can be used.

As a method not using these additives, a method of forcibly injecting carbon dioxide gas into a liquid material using a commercially available gas mix system to obtain a uniform foam can also be used.

By adding the organic filler of the vinyl chloride sol-based undercoat composition of the present invention, the independent formation of foam cells in the cured film can be maintained and the generation of blisters can be effectively prevented.

As the organic filler, it is preferable to use one or more organic powders selected from acrylic resin, styrene resin, xylene resin, phenol resin, polypropylene resin, polyethylene resin and polyamide resin. . In particular, a material that absorbs the plasticizer during baking in the plasticizer is preferable.

In order to further improve the ability to absorb the impact sound of stepping stones, it is necessary to soften the cured film to form appropriate closed cells. Adjustment and uniformity of the foam cells are most important in obtaining a foam film by using a foaming agent in the PVC resin sol paste. By further containing a cell conditioner in the undercoat composition,
It is possible to form an appropriate closed cell.

The PVC underwater soundproof undercoat of the present invention can be used under the same line conditions and baking conditions as those used in the conventional undercoating of an automobile coating line. Coating is performed by normal airless spray, 140 ° C ~
By heating at a baking oven at 150 ° C. for 20 to 30 minutes, it is possible to obtain a coat film having uniform foaming properties and without impairing the appearance quality.

The undercoat composition of the present invention having the above-described structure is applied to a predetermined portion of an automobile body, for example, a wheel house, a locker portion, a floor back, etc., to obtain an automobile body structure having an improved soundproofing effect.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the vehicle body structure of the present invention will be described with reference to FIG. In FIG. 1, 2
Denotes an automobile body, and a drive mechanism is omitted. The undercoat composition of the present invention is applied to the wheel houses 4 and 4, the locker section 6 and the floor lining 8. By applying in this manner, the soundproofing property and the chipping resistance of the automobile body 2 are significantly improved.

[0031]

The present invention will be described below with reference to working examples of the undercoat composition of the present invention. Examples 1 to 3 and Comparative Examples 1 to 3 The undercoat compositions shown in Table 1 were prepared, and their performances were tested for the items shown in Table 1 and the results are shown in Table 1.

The composition of Example 1 was applied to a 30 cm square electrodeposition coated steel sheet as shown in FIG. 3 by an airless spray pump (king type) so as to have a thickness of 2 mm. The sprayability was good, the pattern width was sufficiently wide, the mist was small, and uniform application was possible. 14 applied test pieces
When it was kept in a thermostat at 0 ° C. for 30 minutes and baked under heating, a foam film was formed and a surface film having a good appearance was obtained.

This test piece is actually applied to a wheel house and a locker portion of an automobile, and a stone jumping sound reduction effect measurement test (substitute test) that can obtain the same test effect (substitution test) as when a test course on a gravel is run is obtained. Test method 7) was performed. As a result, the hitting sound was reduced by about 10 dB as compared with the conventional PVC-based (non-foaming type) undercoat, and the effect of reducing the stone jumping sound was recognized. When a chipping resistance test was performed in the above foamed state, it was confirmed that the chipping resistance was sufficient.

A test piece applied in the same manner was used for 30
After standing for 3 days under the condition of 80 ° C and 80% RH, or 110 ° C x
After baking for 10 minutes, left for 3 days under conditions of 30 ° C. and 80% RH, kept in a constant temperature bath at 140 ° C. for 30 minutes, and baked by heating. As a result, a foamed film was formed, and all films having good appearance were obtained. Was. When the tests of Examples 2 and 3 were performed in the same manner, the same good results as in Example 1 were obtained.
In the case of Comparative Example 1 from which calcium oxide was removed and Comparative Examples 2 and 3 in which urea not subjected to treatment was used as a foaming aid, similarly, after leaving at 30 ° C. and 80% RH for 3 days, 140 ° C.
When baking was performed for 30 minutes, generation of blisters was confirmed.

[0035]

[Table 1]

(Note) in Table 1 is as follows. (1): Vinyl chloride resin manufactured by Kanegafuchi Chemical Industry Co., Ltd. (2): Plasticizer manufactured by Sekisui Chemical Co., Ltd.

(3): Calcium carbonate manufactured by Maruo Calcium Co., Ltd. (4): Acrylic resin powder manufactured by ZEON CORPORATION (5): Foaming agent manufactured by Otsuka Chemical Co., Ltd.

(6) Urea (no treatment) (7) Urea treated with stearic acid (amount of stearic acid: 3%) (8) Urea treated with stearic acid (amount of stearic acid: 5%) (9): New Daiichi PVC ( Co., Ltd. cell conditioner (10): Omi Chemical Industry Co., Ltd. calcium oxide

The test method in Table 1 is as follows. 1. Viscosity At 20 ° C, BH type viscometer, rotor No. 7,20 rp
m.

2. Sprayability Using an airless spray pump (King type) manufactured by Nippon Gray Co., Ltd., pressure before gun 100 kg / cm ² , nozzle #
When applied with 537, a good pattern width can be obtained, and there is little tail and mist and there is no uneven coating. ：: Good pattern width, tail, no mist, no coating unevenness △: Pattern width slightly narrow, tail, mist slightly x: Pattern width does not spread, coating unevenness is severe and uniform coating cannot be performed

3. Sagging property Apply the sample on a 150x70x0.8mm electrodeposited plate in the form of a bead with a radius of 5mmx100mm, place it vertically and leave it at room temperature for 30 minutes, then heat it in a dryer at 95 ° C for 8 minutes After removal, the sag (mm) is measured.

4. Adhesiveness A sample is applied to the end of an electrodeposited plate of 100 × 25 × 1.0 mm, and a spacer is sandwiched and fixed so that the film thickness of the bonded portion becomes 3 mm, followed by heat baking at 140 ° C. for 20 minutes. After taking out, remove the spacer and pulling speed 5
The shear adhesion is measured at 0 mm / min. ：: Cohesive failure in fracture state △: Partial fracture in fracture state ×: Full fracture in fracture state

5. Chipping resistance A sample is placed on a 150 × 70 × 0.8 mm electrodeposited coated plate.
Baking at 140 ° C. for 30 minutes at et 1 mm. After returning to room temperature, remove the M4 brass nut from a height of 2 m to a diameter of 5 mm.
The coating film is dropped continuously until a hole reaching the substrate is made. The angle of the test piece is 60 °.

6. Foaming rate Sample was placed on a 30 × 70 mm aluminum plate with a radius of 5 mm × 5
It is applied in a 0 mm semi-circular bead shape, and the volume change before and after baking at 140 ° C. for 30 minutes is measured by an underwater displacement method.

7. Measurement of Stone Bouncing Sound Reduction Effect As shown in FIG. 2, a vinyl pipe having an inner diameter of 25 mm and a length of 2 m is placed on a fixed frame inclined at 45 ° so that a hard sphere falls at the center of the sample. Then, the hard spheres are dropped one by one, and the impact sound generated when the ball and the undercoat surface are impacted is measured. The microphone position is 200mm right from the center of the panel surface and 40mm from the center of the pipe.
(Height 150 mm).

Hard ball; steel ball [8 mmφ (2.0
8g)] A 1.6 t × 300 × 300 mm steel plate is replaced with an outer diameter of 300 ×
It is sandwiched between steel frames of 300 mm, inner diameter 200 × 200 mm and thickness 20 mm. The area of the sample (undercoat)
190 × 190 mm, ChA single mode (800 lines), frequency range 10 KHz, capture window function, rectangular window, trigger at the center of the panel, average 8 times. Frequency analysis 1/3 octave, A characteristic correction.

Test Panel Size and Shape As shown in FIG. 3, a material was applied to the center of a 300 mm × 300 mm ED plate at 190 mm × 190 mm. Mask 55mm from each end. The film thickness of the material is made to be 2 mm in wet film thickness (each n = 1).

8. Visual observation is made as to whether blisters have formed on the homogeneous surface of the foam cells or whether a uniform foam layer has been formed. Conditions (1) A wet 2 mm thick coating is applied on the electrodeposited plate and baked at 140 ° C. for 20 minutes. Condition (2) Wet on electrodeposited plate with 2mm thickness, 30 ℃, 80% R
After leaving H × 3 days, baking is performed at 140 ° C. × 20 minutes. Condition (3) A wet 2 mm thick coating is applied on the electrodeposited plate, baked at 110 ° C. for 10 minutes, then left at 30 ° C. and 80% RH for 3 days, and then 140
Bake at 20C for 20 minutes. ：: No blisters generated △: Blisters slightly generated ×: Blisters generated

[0049]

As described above, the undercoat composition of the present invention is applied in the summer, when it is applied and left as it is for 2 to 3 days, or baked in a sealer drying oven, and thereafter,
When left for days, the blister does not occur in the middle coat drying oven, forming a uniform foam cell layer and surface coating layer, increasing the shock absorption capacity and imparting the soundproofing function to increase the coating weight. It is possible to obtain chipping resistance (rustproofing) and soundproofing performance without causing noise, and to provide a great effect that noise caused by stones, sand, etc., which are rolled up from tires while the vehicle is running can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an automobile body structure according to the present invention.

FIG. 2 is an explanatory view showing a stone jumping sound measuring device.

FIG. 3 is a plan view showing a test panel in the rock splash sound measuring device.

[Explanation of symbols]

2 car body, 4 wheel house, 6 locker section,
8 Floor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 7/12 C09D 7/12 Z (72) Inventor Masao Takahashi 4-5-9 Higashi Gotanda, Shinagawa-ku, Tokyo Semedine Co., Ltd. (72) Inventor Yutaka Ohashi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tsutomu Ochi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (8)

[Claims] 1. A urea or urea system containing a vinyl chloride resin, a plasticizer, a calcium carbonate powder, a foaming agent, a foaming aid, and a moisture absorbent as essential components, and treated with a fatty acid as the foaming aid. A vinyl chloride plastisol-based undercoat composition comprising a compound. 2. The vinyl chloride plastisol-based undercoat composition according to claim 1, further comprising an organic filler. 3. The vinyl chloride plastisol-based undercoat composition according to claim 1, further comprising a cell conditioner. 4. The method according to claim 1, wherein one or more plasticizers selected from phthalic acid, polyester, sulfonic acid and phosphoric acid are used as the plasticizer.
4. The vinyl chloride plastisol-based undercoat composition according to any one of claims 1 to 3. 5. An acrylic resin as the organic filler,
Xylene resin, phenol resin, polypropylene resin,
The vinyl chloride plastisol-based undercoat composition according to any one of claims 2 to 4, wherein one or more organic powders selected from a polyethylene resin and a polyamide resin are used. 6. The calcium carbonate having an average particle size of 0.0
The thickness is 3 to 0.07 µm.
A vinyl chloride plastisol-based undercoat composition according to any one of the preceding claims. 7. An automobile body structure wherein the undercoat composition according to any one of claims 1 to 6 is applied to a predetermined portion to enhance a soundproofing effect. 8. A method for improving the soundproofing performance of an automobile body by applying the undercoat composition according to claim 1 to a predetermined portion of the automobile body.