JP4331046B2 - Damping material - Google Patents

Description

  The present invention relates to a material used for damping, and more particularly, to a damping material suitable for being applied by application to a site where vibration is transmitted.

In vehicles, particularly passenger cars, less noise and vibration during vehicle travel leads to improved riding comfort and environmental considerations. For this reason, it is common to lay damping materials on doors, trunk rooms, floors, dash panels, and the like. Conventionally, a sheet mainly composed of asphalt has been used as a vibration damping material. However, when laying this sheet, it is cut according to the shape of the installation surface, temporarily fixed to a curved surface or a surface close to vertical, a predetermined The placement at the position is a manual operation. For this reason, damping materials that can be laid by coating have been developed in order to reduce the number of processes or to be automated by a robot or the like.
The coating type vibration damping material has a resin emulsion as a main component. For example, a composition mainly composed of a mixture of aqueous asphalt and vinyl acetate emulsion (for example, see Patent Document 1), or an acrylic emulsion in which a core part and a shell part are formed by different acrylics is a major component. An application-type vibration damping material (see, for example, Patent Document 2) is disclosed. In addition, a composition containing an acrylic emulsion, a vinyl acetate emulsion, or a copolymer emulsion of acrylic styrene or vinyl acetate and a heat-expandable organic hollow filler (see, for example, Patent Document 3), a synthetic resin or A vibration-damping coating composition comprising resin powder and an inorganic filler in an asphalt emulsion (see, for example, Patent Document 4), an acrylic ester copolymer and / or an ethylene-vinyl acetate copolymer emulsion comprising a polymer An aqueous vibration-damping paint containing a thickener and / or a dispersant (see, for example, Patent Document 5) is disclosed. Also, a water-based soundproofing paint containing any two of acrylic acid ester polymer, styrene-butadiene copolymer, or styrene-acrylic acid ester copolymer and barium sulfate as an inorganic filler (see, for example, Patent Document 6) .) Is disclosed.

JP-A-9-328594 JP 2000-86939 A JP 7-145331 A JP-A-9-104842 Japanese Patent Laid-Open No. 9-151335 JP 2001-64545 A

However, if the polymers contained in these vibration damping materials are used alone, it is difficult to obtain good vibration damping properties over a wide temperature range required for vehicles, particularly 20 ° C to 60 ° C. For this reason, in order to impart vibration damping properties, a plurality of polymers must be blended, and the composition must be complex.
Accordingly, an object of the present invention is to provide a vibration damping material having a good vibration damping property in a wider temperature range with a smaller number of raw materials.

This onset bright for solving the above problems, as a synthetic resin component, a damping material mainly containing polylactic acid resin emulsion.
According to the present invention, in the damping material, the maximum value of the loss tangent value, which is one measure of damping performance, is in the vicinity of the glass transition temperature, and the maximum value is specifically compared with other resins. Contains a large polylactic acid resin prepared in an emulsion. For this reason, as in the case of known vibration damping materials, not only low temperatures of less than 20 ° C. (for example, 0 ° C. or more and less than 20 ° C.), but also a wider temperature range, for example, higher temperature range of 20 ° C. to 60 ° C. In addition, it is a vibration damping material that exhibits vibration damping properties due to the polylactic acid resin. Therefore, it is a vibration damping material having a good vibration damping property in a wider temperature range with a smaller number of blending species.
The front Symbol polylactic acid resin emulsion, Ru der loss tangent value at the glass transition temperature of 1.0 or more.
According to the present invention, a damping material comprising a polylactic acid resin emulsion having a glass transition temperature in a temperature range in which the damping property is surely good at least near the glass transition temperature and the damping property is desired to be exhibited. By selecting, it is possible to obtain a good vibration damping property at a desired temperature.
This onset Ming, Ru formable der in a film form by drying the coated fabric.
According to the present invention, the damping material can be laid by applying a damping material to a desired portion by coating, and the damping material can be easily adhered to the portion to be damped and applied.
In addition, the present invention contains a polylactic acid resin emulsion, an inorganic filler, a polysaccharide thickener, and a wax .
According to this vibration damping material, the vibration damping property in a wider temperature range from a low temperature such as −10 ° C. to 60 ° C. or higher is good due to the polylactic acid resin, and dripping and drying after coating. A vibration damping material can be obtained that suppresses the swelling of the time and adheres well to the part to be damped.

  According to the present invention, by providing a vibration damping material having a good vibration damping property in a wider temperature range with a smaller number of raw materials, various methods can be used by a simpler preparation process or by a method similar to the conventional method. Therefore, it is possible to obtain a vibration damping material having good vibration damping properties in a wider temperature range.

The best mode for carrying out the present invention will be described below.
The vibration damping material of the present invention is typically one that can be formed into a film shape on a portion to which a vibration damping material is to be applied, and can be formed by heating, drying, or the like as appropriate. That is, it is suitable as a vibration damping material in which a film-like vibration damping material is formed by coating, but because of its good fluidity, it is appropriately mixed with asphalt or other resin materials to produce the vibration damping material. You may use as a raw material for.

The vibration damping material of the present invention mainly contains a polylactic acid resin emulsion as a synthetic resin component.
The polylactic acid resin emulsion is a fluid having a polylactic acid resin as a dispersoid, and the dispersion medium may be an organic solvent such as alcohol, but is typically water. In the case of water, it is possible to suppress deterioration of the working environment when the vibration damping material is dried to obtain a vibration damping material, which is preferable. The concentration of the polylactic acid resin emulsion is not particularly limited, but the mixing ratio of the polylactic acid resin to water is preferably 2: 1 to 1: 2, more preferably from the viewpoint of handling such as mixing with other materials. The mixing weight ratio of water: polylactic acid resin is 1: 1.

  The polylactic acid resin dispersed in the polylactic acid resin emulsion contains a resin including a polymer chain having a lactic acid unit. That is, the polylactic acid resin is a polymer having a lactic acid unit or a polymer mixture in which a predetermined amount of a predetermined additive is added to the polymer, and is a polylactic acid homopolymer, a polylactic acid copolymer, or a polylactic acid blend. It is. The polylactic acid resin emulsion contains at least one of polylactic acid homopolymer, polylactic acid copolymer, or polylactic acid blend.

  The polylactic acid homopolymer may be a polymer composed only of either D-lactic acid or L-lactic acid, but is preferably a polymer having low crystallinity, and therefore a polymer in which D-lactic acid and L-lactic acid are mixed is preferable. . For example, the abundance ratio of D-lactic acid and L-lactic acid is preferably in the range of L / D = 75/25 to 25/75 in terms of molar ratio, since the crystallinity becomes sufficiently low. The production method of the polylactic acid homopolymer is not particularly limited, and direct dehydration condensation of lactic acid monomers, lactic acid dimer L-lactide (two L-lactic acid cyclic dimers), D-lactide (two D-lactides) A cyclic dimer of lactic acid) and meso-lactide (a cyclic dimer of D-lactic acid and L-lactic acid). Thereby, a homopolymer of D-lactic acid or L-lactic acid or a copolymer of D-lactic acid and L-lactic acid is obtained.

  The polylactic acid copolymer is a polymer obtained by polymerizing lactic acid or lactide and another component such as a monomer or dimer other than these, or a polymer. Typically, the polylactic acid copolymer is preferably a copolymer in which 50% or more of the structural units are lactic acid units. The other component polymerized with lactic acid is a group of molecules that can form a molecular chain of polyester by polymerization. Examples of such molecular groups include dicarboxylic acids and polyhydric alcohols, hydroxycarboxylic acids, lactones, and polymers having these groups at the ends, such as polyesters, polyethers, and polycarbonates.

Specific examples of the dicarboxylic acid include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, and isophthalic acid.
Examples of the polyhydric alcohol include aromatic polyhydric alcohols such as those obtained by addition reaction of bisphenol with ethylene oxide, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, Examples include aliphatic polyhydric alcohols such as neopentyl glycol, and ether glycols such as diethylene glycol, triethylene glycol, polyethylene glycol, and polypropylene glycol.
Examples of the hydroxycarboxylic acid include glycolic acid, hydroxybutylcarboxylic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, hydroxyheptanoic acid, and the like. Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β-butyrolactone, γ-butyrolactone, pivalolactone, and δ-valerolactone.

  In addition, the manufacturing method of polylactic acid-type resin is not specifically limited, A well-known various method can be used. Examples of preferred methods include JP-A-7-33861, JP-A-59-96123, Proceedings of the Polymer Discussion 44, 3198-3199, US Pat. No. 4,057,537, published European Patent Application No. 261572. No., Polymer Bulletin, 14, 491-495 (1985), Makromol Chem. , 187, 1611-1628 (1986), JP-A-7-247345, and the like. Since these are known methods, a detailed description thereof is omitted.

The molecular weight of the polylactic acid homopolymer or polylactic acid copolymer is not particularly limited as long as it can be prepared into an emulsion. Of the polylactic acid polymer, the amorphous portion contributes to vibration damping properties, and therefore may have a relatively small molecular weight. However, polylactic acid resins having a weight average molecular weight of 100,000 or more are preferable because they are more stable and have good durability against hydrolysis. On the other hand, from the viewpoint of preparation into an emulsion, a polylactic acid resin having a weight average molecular weight of 500,000 or less is preferable because it can be easily prepared in an emulsified state. Therefore, the polylactic acid polymer preferably has a weight average molecular weight of 100,000 or more and 500,000 or less.
In addition, the polylactic acid homopolymer or the polylactic acid copolymer is an unreacted monomer or a component having a low molecular weight, for example, a molecular weight of 2000 or less, from the viewpoint of stability, that is, the obtained vibration damping material and the life of the vibration damping material. Is preferably 3000 ppm or less in the polylactic acid resin.

  The polylactic acid resin may be a polylactic acid blend obtained by adding a control component for controlling the glass transition temperature to a polylactic acid homopolymer or a polylactic acid copolymer. The control component is a component that increases or decreases the glass transition temperature of the resin by being blended with the polylactic acid resin, and the polylactic acid homopolymer or polylactic acid copolymer in which the control component is dispersed is a single component. It shows a different temperature behavior. Examples of the control component include known plasticizers and terpene phenol copolymers. For example, the general glass transition temperature of poly-L-lactic acid is around 60 ° C., but the poly-L-lactic acid blend added with tributyl acetylcitrate in a ratio of 100: 20 has a glass transition temperature of about 25. ° C.

  The plasticizer is blended with the polylactic acid homopolymer or polylactic acid copolymer to lower the glass transition temperature. As the plasticizer, known plasticizers can be used. For example, lactic acid derivatives, aromatic dibasic acid esters, aliphatic dibasic acid esters can be used, and phthalic acid esters, adipic acid esters, glycols can be used. Acid derivatives, ether ester derivatives, glycerin derivatives, alkyl phosphate esters, dialkyl ethers, diesters, tricarboxylic acid esters, polyesters, polyglycol diesters, alkyl alkyl ether diesters, aliphatic diesters, alkyl ether monoesters, citrate esters, aromatic One or more selected from the group consisting of hydrocarbons can be used. Phthalic acid diesters and ether esters can be preferably used. More specifically, one or two selected from the group consisting of dimethyl phthalate, diethyl phthalate, ethyl phthalyl ethyl glycolate, triethylene glycol diacetate, dipropylene glycol dibenzoate, tributyl acetyl citrate, and triacetin It is preferable to use the above. Moreover, since the solubility parameter (SP (σ) value) of polylactic acid is around 9.7, a plasticizer having a solubility parameter close to the solubility parameter of polylactic acid is highly compatible, preferable. Accordingly, a plasticizer having an SP (σ) value in the range of 9.0 to 11.0 is preferable, and if it is less than 9.0 or exceeds 11.0, the mixed state tends to be unstable. More preferably, a plasticizer in the range of 9.5 to 10.5 is used.

The plasticizer preferably has a weight average molecular weight of 100 to 5000 in order to improve slippage between the molecular chains of the polylactic acid homopolymer or polylactic acid copolymer. A plasticizer having a weight average molecular weight of less than 100 is too small to obtain a good plasticizing effect. A plasticizer having a weight average molecular weight of more than 5000 is too large, and particularly liquefaction and vaporization are poor. It is difficult to achieve good dispersion between molecular chains, and it is difficult to obtain a good plasticizing effect. More preferably, the weight average molecular weight of the plasticizer is 200 to 3000.
The amount of the plasticizer added to the polylactic acid-based resin is not particularly limited, but is preferably 5.0 parts by weight or more and 30.0 parts by weight or less based on the polylactic acid-based resin. The glass transition temperature can be significantly lowered while maintaining the properties derived from.

The terpene phenol copolymer is a copolymer obtained by copolymerization of a natural or synthetic cyclic terpene and a phenol. More specifically, the following copolymers can be mentioned.
a) A cyclic terpene / phenol 1 mol / 2 mol adduct added at a ratio of 2 molecules of phenol to 1 molecule of cyclic terpene.
b) Polycyclic terpene / phenol 1 mol / 2 mol adduct obtained by condensation polymerization of cyclic terpene / phenol 1 mol / 2 mol adduct with aldehydes or ketones.
c) Polycyclic terpenes / phenols obtained by polycondensing cyclic terpenes / phenols 1 mol / 1 mol adducts added at a ratio of 1 molecule of phenols to 1 molecule of cyclic terpenes with aldehydes or ketones 1 mol / 1 mol adduct.
It is preferable to contain at least one of these as a main component, and other terpene phenol copolymers may be included. Further, a terpene polymer may be contained, and the terpene polymer may be used alone or mixed with one or more terpene phenol copolymers.

  The terpene phenol copolymer has the effect of increasing or decreasing the glass transition temperature depending on the addition form of the phenol. Typically, a terpene phenol copolymer that raises the glass transition temperature is a copolymer that can maintain a solid state at room temperature. Such a terpene phenol copolymer can be obtained, for example, by adding phenols to terpenes by Friedel-Crafts reaction. For example, 0.1 to 12 mol of phenol is added to 1 mol of cyclic terpene. Can be added. In a polylactic acid resin to which such a terpene phenol copolymer is added, particularly polylactic acid, since the formation of polylactic acid crystals is inhibited by the presence of the terpene phenol copolymer, the glass transition temperature rises. Thereby, it becomes a polylactic acid type resin having higher vibration damping properties at higher temperatures.

  The terpene phenol copolymer that lowers the glass transition temperature is typically a copolymer that can maintain a liquid state at room temperature. Such terpene phenol copolymers are obtained, for example, by adding phenols to terpenes by an acid addition reaction. For example, 0.5 to 6 mol of phenol is added to 1 mol of cyclic terpene. Can be added. In the polylactic acid-based resin to which such a terpene phenol copolymer is added, the slip of the polylactic acid-based resin is improved and the glass transition temperature is lowered as in the case of adding a plasticizer.

  The addition amount of the terpene phenol copolymer to the polylactic acid resin is preferably in the range of polylactic acid / terpene phenol copolymer = 30/80 to 90/10 in weight ratio. When the ratio of the terpene phenol copolymer is less than 10% with respect to the total weight of the polylactic acid, inhibition of crystal formation by the terpene phenol copolymer and a decrease in the glass transition temperature do not appear so much. On the other hand, if the ratio of the terpene phenol copolymer exceeds 80% with respect to the total weight with the polylactic acid, the loss tangent value derived from the polylactic acid resin is lowered, and it is difficult to obtain good vibration damping properties. The terpene phenol copolymer also has an adhesion improving performance and can contribute to an improvement in the fixing strength of the vibration damping material to the laying site.

A polylactic acid blend is obtained by mixing a plasticizer or a terpene phenol copolymer with a polylactic acid homopolymer and a polylactic acid copolymer by a known mixing method or the like.
The active reaction catalyst present in the polylactic acid resin is preferably 0.01% by weight or less in the polylactic acid resin. Thereby, the vibration damping material and the vibration damping material can be made to have a long life. Specifically, the active reaction catalyst is in the range of 0.0001 to 0.01% by weight in the polylactic acid resin. The Furthermore, polylactic acid homopolymers or polylactic acid copolymers and polylactic acid blends in polylactic acid-based resins are treated with carboxydiimide, epoxide, oxazoline, oxazine, aziridine, diol, long-chain alcohol, isocyanate, etc. May be. In the polylactic acid-based resin in which the carboxyl terminal is sealed, hydrolysis resistance or biodegradation resistance is improved, and water resistance and durability are good.

  The vibration damping performance of the polylactic acid-based resin largely depends on the amorphous part that does not constitute a crystal. For this reason, it is preferable that the polylactic acid-based resin is not high in crystallinity, and the polylactic acid has a small number of crystal parts to the extent that it does not have a melting point at 80 ° C. or less, that is, has a lot of amorphous parts where the thermal energy required for melting is not constant. Based resins are preferred. More preferably, it is a polylactic acid resin having no melting point. A polylactic acid resin having a melting point exceeding 80 ° C. or substantially absent has a sufficiently large loss tangent value that is an index of vibration damping performance.

Here, the loss tangent value (tan δ) of the polylactic acid resin in the present specification is a value calculated by the following formula.
Tanδ = G "/ G '
Here, G ′ is a storage elastic modulus, G ″ is a loss elastic modulus, and a storage elastic modulus and a loss elastic modulus are values obtained by performing dynamic viscoelasticity measurement according to JIS K7244 under the following test conditions.
Test piece shape: L55mm × W10mm × D1mm
Temperature increase rate: 5 ° C./min, strain: 0.05%, frequency: 1 Hz, test temperature: −50 ° C. to 200 ° C.

It is preferable that the maximum value of the loss tangent value of the polylactic acid-based resin is 1.0 or more because vibration damping properties are imparted satisfactorily. More preferably, the maximum value of the loss tangent value of the polylactic acid resin is 2.0 or more.
The temperature at which the loss tangent maximum value of the polylactic acid-based resin is not limited, but preferably has a maximum loss tangent value in the range of 0 ° C. or more and 80 ° C. or less, for example. In this case, the vibration damping performance in the temperature range from room temperature, that is, from the normal outside air to the time when the vehicle is running is good. For polylactic acid resins, especially polylactic acid, it is known that the maximum value of the loss tangent value is at or near the glass transition temperature, and there is a maximum value of the loss tangent value by selecting the glass transition temperature. The temperature range to be performed can be specified to some extent.

  That is, by using a polylactic acid resin having a glass transition temperature in the vicinity of a predetermined temperature that requires vibration damping, the vibration damping in the vicinity of the predetermined temperature can be improved. Therefore, for example, as a vibration damping material for vehicles, a vibration damping material containing a polylactic acid resin having a glass transition temperature of 0 ° C. or higher and 80 ° C. or lower is more preferable. Even more preferably, if the vibration damping material contains a polylactic acid resin having a glass transition temperature of 20 ° C. or more and 60 ° C. or less, the vibration damping performance near the temperature during vehicle running is improved, and vibration during running is reduced. Suitable for suppression.

  The method for preparing the polylactic acid resin emulsion is not particularly limited, and can be prepared by a known method. For example, a method of dissolving a polylactic acid resin in an organic solvent, adding an emulsifier, and then gradually adding water, dissolving a polylactic acid resin in an organic solvent, mixing the water to which the emulsifier is added, Can be prepared by a method of adding lactic acid, a method of melting and mixing a polylactic acid resin and an emulsifier, and adding warm water. Of course, a quenching process from a high temperature environment or a pressurizing process may be appropriately added to these methods. In addition, the organic solvent which can melt | dissolve a polylactic acid-type resin can use a chlorine-type solvent, an ester solvent, a ketone-type solvent, an aromatic solvent etc., for example, chloroform, ethyl acetate, acetone, toluene etc. are favorable. Can be used for These solvents can be removed by volatilizing the polylactic acid resin into an aqueous emulsion and volatilizing it appropriately under reduced pressure. The vibration damping material from which the solvent is removed is preferable because deterioration of the working environment during use is suppressed.

  The emulsifier used to prepare the polylactic acid emulsion is a known emulsifier, and any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant is used. can do. Examples of emulsifiers that can be used favorably include alkyl sulfates, polyoxyethylene alkyl ether sulfates, sulfosuccinates, N-acyl amino acid salts, carboxylates, sulfonates, and phosphoric acids among anionic surfactants. Esters can be used, and alkyl ammonium salts and the like can be used among cationic surfactants. Among amphoteric surfactants, alkyl (amido) betaine, alkyldimethylamine oxide, etc. can be used favorably. Examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, Oxyethylene alkylamine ether, polyoxyethylene aliphatic ester, sucrose fatty acid ester and the like can be used favorably. These may be used alone or in combination of two or more surfactants having the same or different ionicity.

It is preferable to add a polysaccharide thickener to the vibration damping material in addition to the polylactic acid resin emulsion. Polysaccharide thickeners can be used favorably to impart good viscosity to the damping material. That is, the viscosity can be increased without impairing the properties of the polylactic acid resin. Polysaccharide thickeners are preferred because they can be obtained from non-petroleum resources such as plant resources and animal resources, and the environmental load is relatively small even when discarded. Suitable polysaccharide thickeners for the damping material are, for example, cellulose derivatives, starch derivatives, plant gums and animal polymers. Specifically, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose and the like as cellulose derivatives, cationized starch, etherified starch and the like as starch derivatives, gum arabic, gua gum, Xanthan gum and the like, and chitin, chitosan and the like are preferable as the animal polymer. The blending amount of the polysaccharide thickener in the vibration damping material is not particularly limited, but is typically a weight equal to or less than the weight of the polylactic acid resin.
In addition, the viscosity of the vibration damping material can be set to a preferable viscosity according to the usage method, for example, the coating method. With polysaccharide-based thickeners, for example, it is easy to adjust the damping material to a viscosity suitable for spray coating.

  Moreover, it is preferable to add wax to the vibration damping material. By adding a wax, at least one component such as surface smoothness, mold release, water repellency, oil resistance, water resistance, solvent resistance, etc., typically all or a plurality of these can be improved. . As the wax, either natural wax or synthetic wax can be used. For example, natural waxes are preferably candelilla wax, carnapa wax, rice bran wax, wood wax, beeswax, paraffin, ceresin, etc., and synthetic waxes are hydrogenated such as modified wax such as polyethylene wax or 1,2-castor oil. Fatty acid amide waxes such as wax, paraffin wax derivative, stearic acid amide, ethylenebishydroxystearic acid amide, 1,2-hydroxystearic acid, phthalic anhydride imide and the like can be suitably used. The blending amount of the wax in the vibration damping material is not particularly limited, but is typically a weight equal to or less than the weight of the polylactic acid resin.

Furthermore, the vibration damping material typically contains an inorganic filler. Various kinds of known inorganic fillers can be used and are not particularly limited. For example, calcium carbonate, magnesium carbonate, barium sulfate, potassium titanate, talc, clay, zinc oxide and other pigments, mica, alumina, diatomaceous earth, plastic balloon, glass balloon, silica balloon, shirasu balloon, carbon hollow sphere, etc. A filler can be used. Among inorganic fillers, pigments and the like are preferably materials whose surface is treated with a fatty acid or the like because they can be well dispersed in the vibration damping material. In addition, when a hollow filler is used, it is possible to reduce the weight by suppressing a decrease in performance of the damping material, which is preferable. The blending amount of the inorganic filler in the vibration damping material is not particularly limited. For example, in the case of a vibration damping material for coating, the proportion is preferably 40% by weight or more and 70% by weight or less. When the inorganic filler is less than 40% by weight, the viscosity is low, and sagging is likely to occur when applied to a vertical surface or the like. On the other hand, when the inorganic filler exceeds 70% by weight, the viscosity increases, and in particular, the spray nozzle may be clogged during spray coating. More preferably, the blending amount of the inorganic filler is 50% by weight or more and 60% by weight or less in the vibration damping material.
In the vibration damping material, other known auxiliary materials such as thickeners, surface smoothing agents, mold release agents, water repellents, rust preventives, antifoaming agents, dispersing agents, anti-settling agents, An ultraviolet absorber, an anti-aging agent, etc. may be contained.

  The vibration damping material is obtained by dispersing and mixing all the materials to be blended. Namely, using known mixing and dispersing machines such as dissolver, Banbury mixer, planetary mixer, glen mill, open kneader, vacuum kneader, polylactic acid resin emulsion, inorganic filler, polysaccharide thickener, wax, etc. It is prepared by dispersing and mixing the secondary materials. At this time, by performing the vacuum defoaming treatment, it is possible to remove the bubbles in the material and to obtain a vibration damping material in which the occurrence of gas bulging or the like is reduced.

  This damping material is used by applying it to a site to be damped or mixing it with a material to be damped by a desired method. Typically, it is used by applying to the site to be damped. The application method of the vibration damping material is not particularly limited, and a known application method such as a brush, a roller, or a spray can be used. Preferably, spray coating is preferable because it can be easily and uniformly applied to a three-dimensional surface such as a curved surface, a fine concavo-convex surface, a deep concave portion, or the like with a desired film thickness. For example, the vibration damping material can be applied along the three-dimensional press shape of a steel plate constituting a trunk room or a floor of the vehicle. The form of spray coating is not particularly limited, and a known spray coating machine such as an air spray gun or an airless spray gun can be used. In the vibration damping material prepared by volatilizing the organic solvent, the deterioration of the working environment is satisfactorily reduced even by spray application, and therefore, spraying in various places is possible. The damping material is solidified by drying and becomes a damping material. In spray coating, a damping material is formed that adheres as a film to a site to be damped by drying.

In the damping material obtained by this damping material, the damping property in the range of 0 to 40 ° C. is secured by the polylactic acid resin as in the case of the acrylic resin or vinyl acetate resin, and the polylactic acid resin Therefore, the vibration damping property in a higher temperature range, for example, 40 ° C. or more and 60 ° C. or less is good. Therefore, the vibration damping material does not need to be provided with a resin material other than the polylactic acid resin for vibration damping performance, and has a simpler configuration. For this reason, it is easy to adjust the viscosity, select a surfactant, and the like, and the vibration damping material has a good vibration damping property in a wider temperature range with a smaller number of components. Also, when using a plurality of resins having different glass transition temperatures, since they are selected from polylactic acid resins, their properties are similar to each other, making it easy to prepare an emulsion, and combining a plurality of completely different materials The cost can be reduced compared to
By adding a polysaccharide thickener and / or wax in addition to the polylactic acid resin emulsion to the damping material as a secondary material, a damping material with good paintability and durability can be obtained. It becomes a vibration material. In this case, the polylactic acid resin, polysaccharide thickener, and wax can all be obtained from non-petroleum resources, and should be a vibration damping material that has a low environmental impact both during production and disposal. Can do.

(Preparation of polylactic acid resin emulsion)
A polylactic acid solution was prepared by dissolving 100 parts by weight of polylactic acid (polylactic acid “5400”, manufactured by Toyota Motor Corporation) in 400 parts by weight of ethyl acetate. To this polylactic acid solution, a nonionic surfactant (Leodol TW-S120V, manufactured by Kao Corporation) and an ionic surfactant (Neopelex G-65, manufactured by Kao Corporation) as an emulsifier are 1: 1. A mixed solution was prepared by adding 10 parts by weight of the mixture mixed at a ratio of and stirring. Next, while stirring this mixed solution with a homogenizer, 100 parts by weight of ion exchange water was gradually added dropwise to prepare an emulsion. The emulsion was left under reduced pressure to volatilize and remove ethyl acetate.
(Preparation of damping material)
Polylactic acid emulsion prepared as described above 40% by weight (solid content 50%), calcium carbonate 40% by weight, mica 10% by weight, Primer TT-615 as an anti-sagging agent, 5% by Rohm & Haas %, Each component was mixed and dispersed with a high-speed stirrer at a blending ratio of 5% by weight of Adecanate B-187 and Asahi Denka Kogyo Co., Ltd. as an anti-dandruff agent to prepare a vibration damping material.
Further, as comparative examples, acrylic emulsion (Cybinol, manufactured by Seiden Chemical Co., Ltd.) 40% by weight (solid content 50%), calcium carbonate 40% by weight, mica 10% by weight, and the same sagging inhibitor 5% by weight as in the examples. Each component was mixed and dispersed with a high-speed stirrer at a blending ratio of 5% by weight of the anti-dandruff agent to prepare a vibration damping material.

(Measurement of loss factor)
A loss factor, which is a measure of damping performance, was determined based on the resonance method (see page 438 of the “Noise Countermeasure Handbook” published by the Japan Society for Acoustic Materials). The test piece was formed by applying the damping material of the example or the comparative example to a steel plate having a thickness of 1.6 mm so that the weight after drying was 4 kg / m ² and drying at 140 ° C. for 30 minutes. A damping material was formed. Loss coefficients at 20 ° C., 40 ° C., 60 ° C., and 80 ° C. were determined. The results are shown in FIG.

  As shown in FIG. 1, the comparative example and the example have almost the same loss factor up to about 40 ° C., but the comparative example has a loss factor of about 0.02 compared to the example when the temperature exceeds 50 ° C. Becomes smaller. This difference was maintained even near 70 ° C., and was a value higher than 0.01 even at 80 ° C. Thus, in the examples, it was found that the loss factor was relatively high even at 50 ° C. to 80 ° C., particularly 50 ° C. to 70 ° C., and the damping performance was good. In particular, the damping material made of the damping material of the example maintains 0.05 or more, which is considered to have significant damping performance up to around 55 ° C., and is controlled in a temperature range of 20 ° C. to 60 ° C. It was found that it functions well as a vibration material.

It is a graph which shows the temperature change of the loss coefficient in the Example and comparative example of this invention.

Claims (3)

As a synthetic resin component, mainly containing a polylactic acid resin emulsion having a loss tangent value at a glass transition temperature of 1.0 or more ,
The polylactic acid resin emulsion is a vibration damping material containing a polylactic acid homopolymer in which D-lactic acid and L-lactic acid are mixed in a molar ratio of L / D = 75/25 to 25/75 .   The vibration damping material according to claim 1, which can be formed into a film by coating and drying. And no machine filler, a polysaccharide thickener, containing a wax, the damping material according to claim 1 or claim 2.

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