JPS631975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for bonding polyurethane elastomers to metals. More specifically, the present invention uses a primer to which a curing catalyst is added instead of a conventional bake-on type primer, that is, a primer that hardens by heating at 100°C for several hours and develops adhesive strength. Method for forming a strong adhesive layer with metal at the same time as curing two-component polyurethane elastomer (Japanese Patent Application Laid-Open No. 56-24425)
This invention relates to a further improved method of.

The present invention uses a two-component polyurethane elastomer that cures at room temperature to 60°C (hereinafter referred to as room temperature curing polyurethane elastomer), and such polyurethane elastomer can be used for building materials such as waterproofing materials, flooring materials, and sealing materials. It is widely used for various purposes, including those that require adhesion to metals. When adhering a cold-curing polyurethane elastomer to metal, various cold-curing primers are used. Generally, isocyanate-based primers, epoxy resin-based primers, wash primers, and silane-based primers are used.
In the case of polyurethane sealants, JP-A-53-
As shown in No. 23335, it is known that by using a silane primer modified with isocyanate or the like, adhesive strength can be sufficiently maintained even when immersed in water. However, in the case of flooring materials with high cohesive strength of polyurethane elastomer,
When using isocyanate-based or epoxy-based primers, initial adhesion is high, but the primer peels off from the metal surface when immersed in water.

On the other hand, hot-cast polyurethane elastomers such as Adiprene and Vulkollan, which are used as materials for industrial parts such as belts, various rolls, and solid tires, often require strong adhesion to metals.
Primers based on modified polyvinyl acetal resins made of formaldehyde condensation type thermosetting resins are widely used, such as AD-1146 and Chemlock+218 from Heusung Chemical Co., Ltd. These primers are so-called baking type primers that develop adhesive strength by heating at 100℃ for several hours, but the polyurethane elastomer bonded to metal using these primers has extremely large agglomerations compared to polyurethane sealants. Despite its strength, in some cases it has such adhesive strength that polyurethane elastomers cohesively break.

Furthermore, it is known that the adhesive strength does not decrease much even when immersed in water or the like.

We have developed a fast-curing polyurethane elastomer composition as shown in JP-A-55-98221, and the urethane elastomer can be cured and demolded in one to ten-odd minutes at room temperature to 60°C. Its mechanical properties and abrasion resistance are fully comparable to hot-cast elastomers such as Aziprene (manufactured by DuPont).

When adhering the above-mentioned fast-curing polyurethane elastomer to metal, apply the above-mentioned baking type primer to the surface-treated metal surface,
If a fast-curing elastomer is applied after baking at 100°C to 120°C for several hours (if cured at room temperature to 60°C), adhesive strength similar to that of hot-cast polyurethane elastomer can be obtained.

However, it is often necessary to bond the fast-curing polyurethane elastomer to metal at the same time as it is cured, and for this purpose a room-temperature curing primer is required. We investigated various types of primers that harden at room temperature, which are used for building materials, etc., but using the baking type primers mentioned above,
Adhesive strength such as that obtained when baking at 100°C to 120°C could not be obtained.

We have applied for patent application No. 54-98687 (Japanese Patent Application No. 1983-
24425), which cures at room temperature to 60℃ and has a high cohesive force equivalent to that of hot-cast elastomers such as adiprene, the elastomer may By using a conventional baking type primer with strong acid added as a room temperature curing type primer that has high adhesive strength to the extent of cohesive rupture, it can be cured at room temperature or 60°C.
It has been found that the desired adhesive strength can be obtained by heating at a temperature of more than ten minutes at °C, and that the adhesive strength does not decrease significantly even when immersed in water.

However, it has been found that the above method has one or two drawbacks.

That is, first of all, the development of adhesive force is slow. For this reason, when removing the molded product from the mold, if too much force is applied to the adhesive interface with the metal, initial peeling may occur.

Second, even when using a fast-curing polyurethane as shown in JP-A-55-98221, if the pot life is set to a long time of around 10 minutes, peeling may occur at part of the adhesive interface with the metal. (hereinafter referred to as the floating phenomenon).

Therefore, the present inventors have investigated various methods for bonding a cold-curing polyurethane elastomer to metal at the same time as curing, which improves the above-mentioned drawbacks.
We have arrived at the present invention.

That is, the present invention provides ``a method for bonding a two-component polyurethane elastomer to metal at the same time as curing, in which a strong acid is added to an organic solvent solution of a polyvinyl acetal resin modified with a formaldehyde condensation type thermosetting resin as a primer. A two-component polyurethane elastomer and a metal, characterized in that the first layer is a solution to which no strong acid is added as the second layer, and the metal surface, the first layer, the second layer, and the two-component polyurethane elastomer are used in this order. ``How to glue them together.''

The polyvinyl acetal resin used in the present invention is obtained by acetalizing polyvinyl alcohol produced by saponifying polyvinyl acetate with formaldehyde, acetaldehyde, butyraldehyde, etc., and has different degrees of acetalization and average degree of polymerization. Various types can be used.

As the formaldehyde condensation type thermosetting resin used in the present invention, known ones such as phenol resin, melamine resin, urea resin, and granamine resin can be used.

The above-mentioned polyvinyl acetal resin and formaldehyde condensation type thermosetting resin are heated and reacted in a solvent to obtain a modified product of the former.

Examples of the organic solvent for dissolving the polyvinyl acetal resin modified by the formaldehyde condensation type thermosetting resin of the present invention include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, alcohols such as methanol, ethanol, and isopropanol, ethyl acetate, Esters such as n-butyl acetate, and other solvents such as toluene, xylene, trichlorethylene, methyl cellosolve, etc. alone or in combination are used.

The concentration of the modified product used is 3 to 30% by weight (hereinafter % refers to % by weight).

Strong acids added as catalysts to the present invention include phosphoric acid and p-toluenesulfonic acid.

The strong acid is a polyvinyl acetal resin modified with a formaldehyde condensation type thermosetting resin.
20% preferably added from 1.0 to 15%.

Metals in the present invention include iron, aluminum, brass, and the like.

The cold-curing two-component polyurethane elastomer of the present invention is not limited to the above-mentioned fast-curing polyurethane elastomer, but includes polyurethane elastomers for civil engineering and construction materials containing various fillers such as calcium carbonate, talc, and clay, rolls, Cast polyurethane elastomers used for various industrial applications such as solid tires, polyurethane elastomers for potting, etc. are also used. Two-part polyurethane elastomers are typically obtained from polyisocyanates and/or polyurethane prepolymers and curing agents that include crosslinking components.

As the polyisocyanate and/or polyurethane prepolymer, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate,
A mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate (65/35,
80/20), diphenylmethane diisocyanate,
Conventionally known aromas such as so-called liquid diphenylmethane diisocyanate, crude product of tolylene diisocyanate, polymethylene polyphenyl polyisocyanate (crude product of diphenylmethane diisocyanate) liquefied by various conventionally known methods such as Japanese Patent Publication No. 38-4576 One or a mixture of two or more of conventionally known alicyclic polyisocyanates such as polyisocyanate, cyclohexylmethane diisocyanate, and isophorone diisocyanate, and/or these various polyisocyanates and various monomeric polyols such as trimethylolpropane, polytetra Methylene ether glycol, various polyether polyols obtained by adding propylene oxide or propylene oxide and ethylene oxide to various monomer polyols, polycaprolactone polyol, various polyester polyols such as polyethylene adipate, 1,2-polybutadiene polyol, castor oil polyol, It is a polyurethane prepolymer with a so-called polymer polyol made by grating vinyl monomer.

These prepolymers may be added with colloidal silica or asbestos to impart thixotropic properties.

As curing agents, monomer polyols such as ethylene glycol, diethylene glycol, 1,4-butanediol, trimethylolpropane, various polyether polyols, various polyester polyols, various polymer polyols, castor oil polyol, 3,3'-dichloro- Aromatic polyamines such as 4,4'-diaminodiphenylmethane and 4,4'-diaminodiphenylmethane, or liquefied aromatic polyamines dissolved in plasticizers, various polyether polyols, etc., or A mixture of two or more types is used.

Further, a plasticizer, a filler such as calcium carbonate, a coloring agent, a thixotropic agent, etc. are added to the curing agent as necessary.

The primer of the present invention can be applied by conventional methods such as brushing, spraying, and pouring. Furthermore, when applying the primer, it is desirable to perform ordinary metal surface treatment methods, such as degreasing, sandpapering, various types of blasting, and various types of chemical treatments, in order to ensure sufficient adhesive strength.

In the present invention, even if too much force is applied to the adhesive interface with the metal when removing the molded product from the mold, initial peeling does not occur, and the pot life is long at around 10 minutes. It was also possible to firmly bond the cold-curing polyurethane elastomer to the metal at the same time as it cured, without causing any floating phenomenon at the adhesive interface with the metal.

Next, the present invention will be explained by giving production examples, examples, and comparative examples. The present invention is not limited in any way by this. Moreover, parts represent parts by weight.

Production of primer stock solution (hereinafter, primer stock solution refers to the solution before addition of a strong acid): - Production example: In a three-necked flask equipped with a stirrer and a reflux condenser, add Denka Butyral + 4000-1 (manufactured by Denka Kagaku Kogyo Co., Ltd.). , polyvinyl butyral resin, average degree of polymerization approximately 920, vinyl butyral 75% by weight or more)
140g, Plyophen 5010 (manufactured by Dainippon Ink & Chemicals, phenolic resin, resol type)
120g, and toluene + isopropanol (1:
Add 790g of mixed solvent (2 weight ratio) and heat at 60℃ to approx.
A homogeneous solution was obtained by heating and stirring for hours. The viscosity is
It was 1350cps/25℃.

Primer application method (Hereinafter, primer refers to a primer stock solution diluted with only an organic solvent or a strong acid added thereto.The former primer is for the second layer in the present invention, and the latter primer is for the main layer. (This is for the first layer in the invention.):- A primer for the first layer is applied with a brush to an iron plate whose surface has been adjusted to a surface roughness of approximately 50μ (JISB 0601) by grit blasting, and after air-drying at room temperature for 30 minutes, A second layer primer was applied and air-dried at room temperature for 1 hour. The dry application amount of each primer is
It was 15-20g/ ^m2 . However, when only the first layer primer was used, the first layer primer was applied twice.

Adhesion test method: - (1) Initial adhesive strength After leaving the adhesive test piece at 25℃ and 55%RH (relative humidity) for 7 days, cut the elastomer into 25mm width and perform a 180 degree peel test at a tensile speed of 50mm/min. I went and asked.

(2) Water-resistant adhesive strength After leaving the adhesive test piece at 25℃ and 55%RH for 7 days, cut the elastomer into 25mm width, immerse it in water at 25℃ for 7 days, and test it at a tensile speed of 50mm/min.
It was determined by performing a 180 degree peel test.

Example 1 Add 1g of primer to 100g of the primer stock solution obtained in the production example.
A solution of 88% phosphoric acid dissolved in 100 g of methyl ethyl ketone was added and stirred uniformly to obtain a first layer primer. Next, the primer stock solution obtained in the production example
Only 100 g of methyl ethyl ketone was added to 100 g and stirred uniformly to obtain a second layer primer.

Hypren Q-583 (Mitsui Nisso Urethane Co., Ltd. polyoxytetramethylene glycol/diphenylmethane diisocyanate prepolymer NCO=
15%) and 0.004 part of dibutyltin dilaurate to 100 parts of Hypren MC-532 (polyoxytetramethylene glycol/diol curing agent manufactured by Mitsui Nichiyo Urethane Co., Ltd.) to reduce the pot life to approximately
Mix the curing agent adjusted to 10 minutes with a two-component polyurethane casting machine (Toho Kikai AF-206 model) at a mixing ratio of 100:66.
(weight ratio), and the mixture was stirred and mixed at a discharge rate of 30 g/sec, and the mixed liquid was discharged so that the elastomer thickness was 5 mm. The iron plate on which the mixed solution had been poured was immediately placed in a curing furnace set at 60°C and cured for 30 minutes to form an elastomer. When we conducted an adhesion test on this specimen, the initial adhesive strength was 20 kg/cm, and the water resistant adhesive strength was
It showed 15Kg/cm, and no floating phenomenon was observed.

Comparative Example 1 Only the first layer primer was used without using the second layer primer (two coats of the first layer primer)
An elastomer was formed by processing in the same manner as in Example 1 except for this.

During curing in a curing oven at 60°C, a floating phenomenon occurred in a considerable part of the adhesive interface.

Example 2 Using primers obtained in the same manner as in Example 1,
It was applied to the core of a urethane solid tire made of iron plate (the surface to which urethane is to be bonded had been adjusted to a surface roughness of about 10 μm (described above) by grid blasting) according to the method described above.

After setting this core in a mold and preheating it at 60°C for 15 minutes, 0.03 part of dibutyltin dilaurate was added to 100 parts of Hyprene Q-583 (mentioned above) and Hypren MC-532 (mentioned above). and a curing agent whose pot life was adjusted to about 1 minute, were stirred, mixed, and discharged using the same two-component polyurethane casting machine as in Example 1 at a blending ratio of 100:66 (weight ratio) and a discharge rate of 50 g/sec. death,
It was poured into a mold.

After 5 minutes of casting, the urethane solid tire was removed from the mold. Although force was applied between the core and the urethane elastomer during demolding, no phenomena such as initial peeling occurred.

Comparative Example 2 Only the first layer primer was used without using the second layer primer (two coats of the first layer primer)
Except for this, a urethane solid tire was cast in the same manner as in Example 2.

When removing the solid tire from the mold 5 minutes after casting, force was applied to the interface between the elastomer and the core, causing peeling at the interface.

Claims (1)

[Claims] 1. In a method of bonding a two-component polyurethane elastomer to metal at the same time as curing, the first layer is an organic solvent solution of a polyvinyl acetal resin modified with a formaldehyde condensation type thermosetting resin and a strong acid is added to the primer. A method for bonding a two-component polyurethane elastomer and a metal, characterized in that the second layer is a solution in which no strong acid is added, and the metal surface, the first layer, the second layer, and then the two-component polyurethane elastomer are used in that order.