KR20050040861A - Underbody sound damping structure for motor vehicles - Google Patents

Abstract

To provide an underbody sound damping structure capable of damping stone chipping with a low cost. An underbody sound damping structure for motor vehicles, characterized by having an acryl-epoxy type heat-cured layer on the coating surface of a steel panel coated with a primer.

Description

Underbody Sound Damping Structure for Motor Vehicles}

The present invention relates to a lower body sound insulation structure of a motor vehicle.

While driving a car, there are often noises of stones splashing due to bumps of stones and the like on the lower body (for example, the floor rear surface A, the wheel house part B, and the sealer C) constituting the lower part of the vehicle body. Occurs. Conventionally, undercoat has been applied to a steel plate coated with a primer on the side or the bottom of a vehicle body for soundproofing and rust prevention from the noise of bouncing of the lower body. Luxury cars are equipped with a resin cover, but in the public car, a resin cover is not used in terms of cost, and an undercoat (for example, polyvinyl chloride (PVC)) is provided. In such public cars, a method of applying an undercoat thickly can be used to increase the rust resistance and at the same time obtain a soundproofing effect at low cost. However, the coating thickness of the undercoat is limited to about 1,200 μm due to liquid dropping, increased body weight, and increased cost. In order to solve this problem, Japanese Patent Laid-Open No. 2-202560 proposes a protective coating for a vehicle body in which a blowing agent is added to the undercoat to thicken the coating film without causing a weight increase. However, as the protective coating for the vehicle body, the foam layer often becomes uneven in the automobile manufacturing process or bubbles are generated on the coating surface. Moreover, even if the usual pressure-sensitive adhesive tape is adhered onto the primer, the adhesive layer may be disadvantageously peeled off due to the plasticizer in the undercoat.

Summary of the Invention

An object of the present invention is to provide a lower body sound insulation structure that can prevent the noise of the stone splashing. The present invention can provide such a structure at low cost.

According to the present invention, there is provided a lower body soundproofing structure comprising an acrylic-epoxy thermoset layer on a coated surface of a steel plate, such as used in automobiles, coated with a primer.

According to the present invention, a lower body for automobiles having a sound insulation performance equivalent to or higher than that of a conventional resin cover and having a higher sound insulation performance than when the undercoat is directly applied to a steel sheet can be produced. The present invention enables such an advantage at low cost.

1 is a cross-sectional view showing an example of the lower body structure of the present invention.

2 is a schematic diagram of a sound level meter.

3 is a graph showing the results of the noise measurement test of each example.

4 is a schematic view of the lower body constituting the lower body.

The vehicle lower sound insulation structure of the present invention comprises a primer coated steel sheet and an acrylic-epoxy cured layer. The steel sheet is usually subjected to primer coating by anionic or cationic electrodeposition coating. Since the acryl-epoxy cured layer has not only antirust property but also adhesion to the intermediate coat and / or top coat, it is not always necessary to undercoat, but undercoat is usually applied on the cured layer.

The acryl-epoxy cured layer is obtained by curing an adhesive film or tape containing an acryl-epoxy curable resin. Pressure-sensitive adhesive tapes or films that can be used to make the lower body soundproofing structures of the present invention can be heat cured at the temperature of the baking step after the undercoat or the intermediate coat and / or the topcoat, for example from 80 to 180 ° C. have. In addition, such films or tapes are required to have chipping resistance (resistance to splashing of the stone) and plasticizer.

The pressure-sensitive adhesive film or tape satisfying the above conditions is a pressure-sensitive adhesive film or tape containing an acrylic polymer, a thermosetting epoxy containing material and a thermosetting agent for the epoxy containing material.

An acryl-type polymer is obtained by carrying out radiation polymerization of an acryl monomer, and is a material which gives the shape of a pressure-sensitive adhesive tape or a film, and gives adhesiveness. For easy molding, the glass transition temperature of the acrylic polymer is preferably from -25 ° C to 200 ° C.

When such pressure-sensitive adhesive tape or film absorbs and retains moisture, the tape or film expands and expands due to an increase in the volume of moisture in the subsequent heating step. This may cause delamination or injury with the steel sheet or the undercoat layer. Therefore, it is preferable that the monomer which comprises an acrylic polymer has the following specific properties. Suitable monomers for the acrylic polymer include radiation polymerizable acrylic monomers containing acrylic monomers which can exhibit solubility parameters of 10 to 14 (cal / cm ³ ) ^0.5 as homopolymers. It is preferable that this acryl-type monomer does not have a nitrogen atom in the molecule. Here, the term "radiation" is used broadly and includes energy rays, such as various types of light, which can cause polymerization of an acrylic monomer by its irradiation. Specific examples thereof include ultraviolet rays and electron beams. In addition, the term "solubility parameter SP" can be defined by following formula (1).

In the above formula, Δe _i is the evaporation energy of each atom or functional group constituting the homopolymer, and Δv _i is the volume of each atom or functional group constituting the homopolymer. The definition of this solubility parameter is described in Polymer Engineering and Science, Vol. 14, No. 2 (February 1974), "A Method for Estimating Both the Solubility Parameters and Molar Volumes of Liquid", by Robert F. Fedors.

The acrylic polymer is preferably contained in an amount of 40 to 250 parts by weight based on 100 parts by weight of the epoxy-containing material. If the content of the acrylic polymer is less than about 40 parts by weight, the pressure-sensitive adhesive tape or film can hardly maintain an effective constant shape, and in many cases becomes vulnerable. On the other hand, when the content of the acrylic polymer exceeds about 250 parts by weight, the thermosetting pressure-sensitive adhesive tape or film does not become sufficiently crosslinked, and heat resistance or final adhesive performance tends to be poor.

It is preferable that the acrylic monomer which can exhibit the solubility parameter of 10-14 (cal / cm <^3> ) ^0.5 as a homopolymer occupies 50-100 weight% of the whole acrylic monomer material. When content of an acryl-type monomer is the said range, not only favorable mixing with a thermosetting epoxy containing material can be implement | achieved, but also favorable mixing with other components for promoting thermosetting of an epoxy containing material can be realized. In addition, the acrylic monomer preferably has a water solubility of 0.2% by weight or less at 25 ° C in addition to the solubility parameter of 10 to 14 (cal / cm ³ ) ^0.5 . By having such water solubility, excellent moisture resistance can be provided with respect to a pressure-sensitive adhesive tape or a film.

More specifically, suitable examples of acrylic monomers include 2-phenoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenyl ethyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxy ethyl acrylate and tri Cyclo [5.2.1.0 ^2,6 ] decanyl (meth) acrylate. These may be used alone or in combination. Among these, the acrylic monomer is more suitably 2-phenoxyethyl acrylate, benzyl acrylate, phenyl acrylate or a combination thereof. In addition, such an acrylic monomer is marketed under the brand names of "Biscoat # 192" and "Biscoat # 160", for example by Osaka Yuki Kagaku.

Due to the excellent moisture resistance derived from the acrylic monomers used, quality control of the pressure-sensitive adhesive tape or film is facilitated, and the pressure-sensitive adhesive tape or film is not exposed to condensation in winter, for example, in a desiccator. It does not need to be stored or preserved with the desiccant. In addition, even if the pressure-sensitive adhesive tape or film is left under conditions of high temperature and high humidity before heat curing of the epoxy-containing material, the tape or film does not substantially absorb moisture.

In the practice of the present invention, in order to produce an acrylic polymer, an acrylic monomer may be combined with other vinyl monomers if necessary. The vinyl monomer which can be used additionally is not particularly limited, but it is (meth) acrylic acid esters having isoalkyl group represented by 2-ethylhexyl acrylate, butyl acrylate, ethyl acrylate or the like, or isobornyl (meth) Acrylate, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, (meth) acrylic acid, 2-methoxyethyl (meth) acrylate, vinyl acetate, and the like. Can be mentioned.

Although an acryl-type monomer generally contains the monofunctional acryl-type monomer which has one vinyl group in 1 molecule as a monomer component, you may contain the polyfunctional acryl-type monomer which has 2 or more vinyl groups in 1 molecule. Examples of polyfunctional vinyl monomers include 1,4-butanediol diacrylate and 1,6-hexanediol diacrylate. It is preferable that a polyfunctional acrylic monomer is normally contained in the quantity of 0-5 weight part with respect to 100 weight part of acrylic monomers.

The acrylic monomers for the acrylic polymer constituting the pressure-sensitive adhesive tape or film can be N, N-dimethylacrylamide, N-vinyl caprolactam, N-vinylpyrrolidone, or acryl, as long as sufficient high moisture resistance can be ensured. It can be used in combination with nitrogen-containing vinyl monomers, such as loyl morpholine and acrylonitrile, and can improve compatibility with an epoxy containing material. For example, 0 to 10 parts by weight of the nitrogen-containing vinyl monomer may be contained with respect to 100 parts by weight of the acrylic monomer.

An acrylic polymer is obtained by superposing | polymerizing the polymerizable monomer containing an acryl-type monomer in presence of a polymerization initiator. It is preferable that the polymerization initiator used here generate | occur | produce a free radical by radiation, such as an ultraviolet-ray, for example. One example of a suitable polymerization initiator is 1,2-dimethoxy-1,2-diphenylethan-1-one, commercially available from Ciba Geigy under the trade name "Irgacure (trade name) 651".

 In the polymerization, a chain transfer agent may be further added in addition to the polymerization initiator to lower the molecular weight of the polymer produced by radiation polymerization of the acrylic monomer. The molecular weight of the acrylic polymer can be controlled by the addition of a chain transfer agent to impart suitable melt-flowability to the adhesive composition. Specific examples of chain transfer agents that can be used include halogenated hydrocarbons such as carbon tetrachloride and sulfur compounds such as lauryl mercaptan, butyl mercaptan, ethanethiol, 2-mercapto ether, and mercapto 3-propionate. .

The thermosetting epoxy containing material contained in a pressure sensitive adhesive tape or film can contribute to the improvement of the final adhesive performance and heat resistance of a pressure sensitive adhesive tape or film. The epoxy containing material which can be used advantageously here is an epoxy resin containing 1 or more of oxirane rings which can superpose | polymerize by ring-opening reaction. Such epoxy containing materials are broadly referred to as “epoxides” and include epoxides in monomeric state and epoxides in polymer state and may be aliphatic, cycloaliphatic or aromatic. Epoxy-containing materials generally have an average of two epoxy groups per molecule, suitably two or more epoxy groups. Such materials are particularly referred to as polyepoxides and include epoxy containing materials with a slightly less functional functionality of 2.0, for example 1.8. The average number of epoxy groups per molecule is defined as the number obtained by dividing the number of epoxy groups in an epoxy-containing material by the total number of epoxy molecules. Polymeric epoxides include linear polymers having epoxy groups at the ends (eg diglycidyl ethers of polyalkylene glycols) and polymers having units of skeletal oxiranes (eg polybutadiene polyepoxides). The molecular weight of the epoxy containing material may vary in the range of about 58 to 100,000. In addition, if necessary, a mixture of various epoxy-containing materials can be used.

In particular, examples of the thermosetting epoxy-containing material include bisphenol A type epoxy resins, bisphenol AD type epoxy resins, bisphenol F type epoxy resins, phenol-novolak type epoxy resins, cresol-novolak type epoxy resins, cycloaliphatic epoxy resins, and triglycerides. Heterocyclic ring-containing epoxy resins such as diyl isocyanate and hydantoin epoxy; Aromatic or aliphatic epoxy resins such as hydrogenated bisphenol-A epoxy resin, propylene glycol-diglycidyl ether copolymer and pentaerythritol-polyglycidyl ether copolymer; Epoxy resin obtained by reaction of alicyclic carboxylic acid and epichlorohydrin; Spiro ring-containing epoxy resins: glycidyl ether type epoxy resins which are reaction products of o (ortho) -allyl-phenol novolac compounds and epichlorohydrin; And glycidyl ether type epoxy resins, which are reaction products of diallyl bisphenol compounds having an allyl group at the ortho position of each hydroxyl group of bisphenol A and epichlorohydrin.

Thermosets are used to thermoset the thermoset epoxy containing materials. Preferably, the thermoset is thermally activated so that the pressure-sensitive adhesive tape or film is exposed to a suitable heat source for a suitable period of time to cure. That is, this thermosetting agent has potential thermosetting at room temperature and can be thermally activated for the first time by heating to perform thermosetting of the epoxy containing material. Suitable examples of thermosetting agents include, but are not limited to, dicyandiamides, organic acid hydrazides, acid anhydrides, salts of Lewis or Brested acids, tertiary amines such as imidazoles or urea derivatives, and the like. As needed, these thermosetting agents can be combined.

In more detail, representative examples of the organic acid hydrazide used as the thermosetting agent include adipic acid dihydrazide; Representative examples of acid anhydrides include phthalic anhydride, trimellitic anhydride and pyromellitic anhydride; Representative examples of salts of Lewis or Brenstead acid include monoethylamine of boron trifluoride and piperidine of boron trifluoride; Representative examples of imidazoles include 2,4-diamino-6- [2'-methylimidazole- (1 ')]-ethyl-s-triazine, 2,4-diamino-6- [2' -Methylimidazole- (1 ')]-ethyl-s-triazine-isocyanurate, 2-phenyl-4-benzyl-5-hydroxyethylimidazole and nickel imidazole phthalate; Representative examples of tertiary amines such as urea derivatives include 3-phenyl-1,1-dimethylurea and 3-p-chlorophenyl-1,1-dimethylurea. Among the above-mentioned thermosetting agents, tertiary amines, such as imidazole or urea derivative, are not normally used alone. Such compounds can be used in combination with dicyandiamide, organic acid hydrazide, or acid anhydrides to function as promoters.

The pressure-sensitive adhesive tape or film may be, for example, a filler made of powder such as calcium carbonate, silica, alumina or talc, a microsphere filler such as silica, a phthalic acid derivative, adipic acid derivative or a plasticizer made of liquid rubber, and an oxidized rubber. Antifoaming agent which consists of an inhibitor, surfactant, and polydimethylsiloxane can be contained.

The material for producing the pressure-sensitive adhesive tape or film may further contain a woven fabric or a nonwoven fabric, if necessary. Such fabrics are impregnated in the material before the pressure-sensitive adhesive tape or film has a uniform shape by radiation polymerization of acrylic monomers, thereby increasing the cohesive force of the pressure-sensitive adhesive tape or film in the longitudinal direction and the width direction, and slitting or stamping. It is easy to work such as to improve the workability. Woven and nonwoven fabrics useful herein are those made from natural or synthetic polymeric fibers, such as polyester, nylon, cotton, polypropylene, cellulose acetate, acetates, combinations thereof, and the like.

The thicker the thickness of the acrylic-epoxy thermosetting layer obtained by curing the acrylic-epoxy thermosetting resin, the higher the noise prevention effect. In order to obtain a sufficiently high effect, the thickness is preferably 0.1 mm or more. However, from the viewpoint of balance between appearance and cost, the thickness of the cured layer is preferably 0.8 to 3 mm.

Examples of commercially available pressure-sensitive adhesive tapes or films that can be used in the present invention include "Tape # 9259 (trade name)" manufactured by Sumitomo 3M.

The underbody is preferably applied with an undercoat to provide rust resistance. In the present invention, any undercoat conventionally used as the undercoat can be used, and for example, polyvinyl chloride, polyurethane or acrylic undercoat can be used. Generally, however, vinyl chloride plastisol is used as the undercoat in view of the balance of cost and performance.

In one embodiment, the undercoat contains a vinyl chloride based resin, plasticizer, filler, tackifier and pigment. As vinyl chloride type resin, the homopolymer of vinyl chloride or the copolymer of vinyl chloride and vinyl acetate can be used, A mixture thereof can also be used as needed.

Plasticizers used herein are commonly used DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (diisodecyl phthalate) or high molecular weight polyesters (adipic acid based polyesters).

The filler may be inorganic fillers such as calcium carbonate, talc and fused silica, which are commonly used, but calcium carbonate is most frequently used in view of workability in coating or coating finish. As tackifiers, block isocyanate or polyamide-based resins, epoxy resins and latent curing agents or mixtures thereof are used in a conventional manner.

As the pigment, carbon black is used as a black pigment, titanium oxide is used as a white pigment, azo, tren or isoindolinone pigment as a yellow pigment, and phthalocyanine pigment is used as a blue pigment. In the present invention, these pigments are appropriately mixed in each of the necessary amounts, blended with the vinyl chloride plastisol composition composed of the above materials, and the color is adjusted to approximate the electrodeposition color.

 Although the vinyl chloride plastisol composition contains the above-mentioned component as a main component, a viscosity modifier and a moisture absorption stabilizer can be mix | blended as needed. Examples of the viscosity modifier include thickeners such as silicic anhydride, hydrous silicic acid, fine calcium carbonate and bentonite. In addition, a reactive diluent may be used in a conventional manner as needed. As the moisture absorption stabilizer, calcium oxide or the like can be used in a conventional manner.

The compounding ratio of the various components in the vinyl chloride plastisol composition is not particularly limited as long as the difference in color or approximation with the electrodeposition coating can be satisfied. Typically, the composition for use in the present invention is 100 to 180 parts by weight of plasticizer, 160 to 180 parts by weight of filler, 2 to 4 parts by weight of tackifier, pigment based on 100 parts by weight of vinyl chloride resin It is obtained by mix | blending 2-10 weight part and 1-4 weight part of other viscosity modifiers.

However, depending on the particle size, the mixing ratio of the vinyl chloride-based resin to be blended, the viscosity of the plasticizer, etc., the relationship between the blending amounts of the above components can be changed within a range that does not cause practical problems. Moreover, other additives can be added as needed.

The thickness of the undercoat is not particularly limited, but is usually 0.1 to 1.0 mm. If the thickness is less than 0.1 mm, there may be a problem in rust resistance, and if it exceeds 1.0 mm, liquid dropping may occur.

Manufacture of Lower Body Soundproof Structures

1 is a cross-sectional view showing one embodiment of a lower body soundproof structure. The lower body soundproof structure 1 has a thermosetting resin layer 3 on the primer coated steel sheet 2 and an undercoat layer 4 thereon. The lower body soundproof structure is a laminate by fixing the acrylic-epoxy thermosetting pressure-sensitive adhesive tape or film on a steel plate coated with a primer, covering the acrylic-epoxy thermosetting pressure-sensitive adhesive tape or film to apply an undercoat Forming, and heating the laminate to cure the acrylic-epoxy thermosetting pressure-sensitive adhesive tape or film, and at the same time can be prepared by the method comprising the step of baking the undercoat. Although not shown, it is also possible to produce a lower soundproof structure without applying an undercoat to the upper surface of the acrylic-epoxy thermosetting pressure-sensitive adhesive tape or film.

The real under structure which laminated | stacked the undercoat layer is more specifically manufactured by the following method.

An acrylic-epoxy thermosetting pressure-sensitive adhesive tape is fixed to a primer coated steel sheet at room temperature, and then an undercoat is applied thereon to obtain a laminate constituting the lower soundproof structure precursor provided with an undercoat layer. In this step, the laminate is heated to a temperature of, for example, 80 ° C. to 150 ° C. for about 5 to 20 minutes, thereby curing the acrylic-epoxy thermosetting pressure-sensitive adhesive film or tape, and simultaneously baking the undercoat, thereby The lower body soundproof structure of is obtained. This structure is further subjected to a single layer topcoat or two layers of intermediate and topcoat coatings. The intermediate coat and the top coat can each be coated by, for example, applying a melamine alkyl paint to a thickness of 20 to 40 μm by electrodeposition. After coating, the intermediate coat and the top coat are usually baked for 20 to 30 minutes at a temperature of 140 to 180 ° C. Therefore, curing of the thermosetting pressure-sensitive adhesive film or tape and baking of the undercoat can be performed by baking of the intermediate coat or the top coat.

Example 1

On an electrodeposited coating plate of 70 mm x 150 mm (hereinafter referred to as "ED coating plate") coated with a primer of 0.8 mm thickness, acrylic-epoxy tape ("Acryl Tape # 9259", trade name, manufactured by Sumitomo 3M Corporation, 1.0 mm thick) ) Was adhered to one entire surface, leaving 15 mm of exposed area from the end in the longitudinal direction. The coated plate was placed in an oven previously set at 140 ° C., left for 20 minutes to cure the resin, cooled to room temperature, and a laminate of the ED coated plate and the thermosetting resin layer was obtained as a sample of this example. This sample is a sealer as the lower body sound insulation structure of the present invention.

Comparative Example 1

The ED coating plate itself described in Example 1 was used as a sample of this comparative example.

Comparative Example 2

20 parts by weight of polyvinyl chloride resin for paste ("G121", trade name, manufactured by Nippon Zeon), 20 parts by weight of vinyl chloride resin for blending ("G103ZX", product name, manufactured by Nihon Zeon), D-2 A plasticizer containing ethylhexyl phthalate ("SANSONIZER DOP", trade name, manufactured by Shin Nihon Rika Sha) 30 parts by weight and 45 parts by weight of calcium carbonate were mixed to form a vinyl chloride plastisol Prepared as an undercoat. The obtained plastisol was applied so as to have a thickness of 1.5 mm on one entire surface of the ED coated plate, leaving the exposed area of 15 mm from the end in the longitudinal direction as in Example 1. The coated plate was placed in an oven previously set at 140 ° C., left for 20 minutes to cure the sol, cooled to room temperature, and a laminate of an ED coated plate and a PVC undercoat layer was obtained as a sample of this comparative example. This sample is a conventional seal-under structure.

Comparative Example 3

PP resin ("Side Garnish", trade name, manufactured by HONDA, 3.0 mm thick) was cut to a size of 70 mm x 150 mm and used as a sample of this comparative example. This sample is a soundproof resin cover generally used as a seal underneath a luxury car.

How to measure noise

2 is a schematic view showing the noise measuring apparatus 10. As shown in Fig. 2, the exposed area 13 of the sample 11 obtained in each example is fixed to stand perpendicular to the jig 12. In addition, the sample of Example 1 orientated so that a thermosetting resin layer might be upward and the sample of Comparative Example 2 may be oriented so that a PVC undercoat layer might be upward. At the point above the diagonal intersection of the sample 11, the positioning pipe 14 was arranged so that the oral 15 could fall from the height of 50 cm above the sample 11 to the sample position. The microphone 16 was arrange | positioned so that the front-end | tip of a microphone may be located in the position of 5 cm just below the dropping position of the oral cavity 15, and this microphone 16 was connected to the personal computer (not shown). 3.5 g oral 15, 3/8 inches in diameter, is dropped from a height of 50 cm, using the real-time octave analysis software (manufactured by Ono Sokki) to measure the frequency range from 500 Hz to 8,000 Hz The noise level was measured at.

Measuring conditions

Frequency: 500 to 8,000 Hz

Measurement data: maximum

Filter: 1/3 octave

Measurement time: 1 second

The results of the test are shown in Table 1 below and FIG. 3. In Fig. 3, the horizontal axis represents the measurement frequency (Hz), and the vertical axis represents the noise level (dB (A)).

From the results of Table 1 and FIG. 3, it can be seen that Example 1, which simulates the seal under structure of the present invention consisting of a laminate comprising an acrylic-epoxy resin layer, has a low noise level at the entire frequency and is the best result. In Comparative Example 1, which consists of an ED coated plate alone, the noise level is the highest in the sound range of 1,000 Hz or higher, indicating that the sound insulation is the worst. In Comparative Example 2, which simulates a conventional seal underlay consisting of a laminate of an ED coated plate and a PVC undercoat, the noise level is low at frequencies above 3,000 Hz, but the noise level is high at low frequencies. In the comparative example 3 which consists of a resin cover used for luxury cars, the noise level was kept low overall.

The lower body sound insulation structure of this invention ensures sound insulation performance equivalent to or more than the conventional resin cover at a very low cost, and at the same time has a sound insulation performance higher than when the undercoat is directly apply | coated to a steel plate.

Claims (4)

An underbody sound insulation structure for an automobile, characterized in that it comprises an acrylic-epoxy thermosetting layer on a coated surface of a steel plate coated with a primer. The undercarriage sound insulation structure according to claim 1, further comprising an undercoat layer on the acryl-epoxy thermosetting layer. The undercarriage soundproof structure for automobile according to claim 1 or 2, wherein the acrylic-epoxy thermosetting layer has a thickness of 0.1 mm or more. The undercarriage sound insulation structure according to any one of claims 1 to 3, wherein the acrylic-epoxy thermosetting layer contains 40 to 250 parts by weight of the acrylic component per 100 parts by weight of the epoxy component.