JPS6056177B2 - Method of bonding parts made of methacrylic ester plastic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION To adhere methacrylic ester plastics to each other or to other plastics, volatile organic solvents are used which are capable of dissolving the plastics.

The solvent swells or dissolves the boundary layer of the plastic parts to be bonded and, upon evaporation under favorable conditions, produces a substantially optically uniform composite. There are countless organic solvents for polymethacrylate, but only a few can be used as adhesives.

The solvent quickly dissolves the plastic surface to be bonded,
It must rapidly obtain sufficient stability to avoid accidental displacement of the bonded parts and cure to an optically clear, bubble-free and tensile strength joint. . Many organic solvents meet only part of this requirement. Many solvents quickly develop high swelling pressures close to the surface.

This is especially true in areas with high tension, e.g. bends.
This produces so-called tensile cracks that run perpendicularly from the adhesive surface. Only a few solvents, such as a few aliphatic chlorohydrocarbons, do not cause tensile cracking. However, much of it evaporates rapidly when it comes into contact with air, and therefore, due to evaporative cooling, the moisture in the air settles in the joint seam, causing permanent turbidity. As the solvent gradually evaporates, the surface of the swollen plastic contracts, often creating air bubbles. In all cases, the tensile strength of the bonded seam is less than the tensile strength of the glued plastic itself, so that the bonded seam tears under load.

Considering these numerous problems, methylene chloride (
dichloromethane) is pointed out as the most suitable adhesive so far for acrylic ester plastics.

Because they rapidly dissolve the plastic and produce a stable joint within 1@, it is often impossible to modify the relative positions of the plastic parts as desired. The conjugate reaches its final strength after two days, but
The edges of the adhesive surface become slightly cloudy.

This phenomenon can only be avoided if the process is carried out in an atmosphere with low absolute humidity. The object of the present invention is to provide an adhesive for methacrylic ester plastics which does not have the disadvantages of known solvents and which produces turbid and bubble-free bonds of high tensile strength.

According to the invention, nitromethane and/or nitroethane are used as adhesives or adhesive additives for methacrylic ester plastics.

Methacrylic ester plastics are polymethyl methacrylate and a major component, in particular more than 8% by weight, is methyl methacrylate and minor components, especially less than 2% by weight, are unsaturated comonomers copolymerizable with it, such as other methacrylic acid ester, acrylic acid ester, styrene, acrylic or methacryl nitrile, vinyl chloride, vinylidene chloride or vinyl ester. The plastic to be bonded should be soluble or at least highly swellable in a suitable organic solvent. That is, all or only some of the plastics to be bonded must be cross-linked. The molecular weight of the plastic plays only a subordinate role with regard to its adhesion potential. Therefore, non-meltable base polymers can be bonded as well as extruded or injection molded plastic parts. The adhesive properties of the injection parts constitute an outstanding feature of the adhesive according to the invention. Nitroethane acts slightly more slowly on methacrylic ester plastics than nitromethane.

As a result, the time for correcting the mutual position of the plastic parts to be bonded after bonding is extended. Due to its high boiling point, nitroethane evaporates more slowly than nitromethane, so that less evaporative cooling occurs and there is less risk of the joint seam becoming cloudy with condensed water even when there is high moisture in the air. This is especially true when nitroethane is used as an adhesive or adhesive additive in admixture with other solvents, such as methylene chloride. Nitroethane can be used in any desired mixing ratio with nitromethane for all the applications described in the literature. The differences mentioned in terms of action and vaporization rate are caused by the mixing ratio. Although nitromethane or nitroethane can each be used alone as an adhesive, it is particularly preferred to use mixtures of nitromethane and/or nitroethane with other volatile organic liquids having a boiling point below 200°C, in particular below 150°C. It's advantageous.

The liquid may be a solvent for the plastics to be bonded and may also be a ketone, ester, ether or aliphatic hydrocarbon such as acetone, cyclohexanone,
Methyl acetate, gotyl acetate, tetrahydrofuran, chloroform, carbon tetrachloride, dichloromethane, dichloroethane, etc. may be used. These solvents alone have the above-mentioned disadvantages as adhesives. At least 30% by weight of nitromethane or nitroethane (calculated relative to the weight of the mixture)
This drawback is significantly suppressed when mixed with That is, the formation of tensile cracks is clearly reduced and the bond strength is increased. The following table lists the adhesive strength of the adhesive member made of extruded acrylic glass after 14 days of adhesion. Nitromethane alone produces a bond strength of 36.6 N/i under the same conditions.

Aliphatic hydrocarbons that alone produce similar high bond strengths, when mixed with nitromethane or nitroethane, yield higher adhesion values than when each component is used alone. Nitromethane or a mixture of nitroethane and dichloromethane (ratio by weight between 30:70 and 80:20) is particularly preferably used in the present invention. Nitromethane or nitroethane is not a solvent for the plastics to be bonded and can also be used in mixtures with organic liquids which do not have their own adhesive action.

The solution can be selected so that it extends the swelling time or the time until stability is achieved, which is desirable in the case of difficult adhesives. This additive may be less volatile than nitromethane or nitroethane. The slow vaporization rate prevents the formation of air bubbles at the joint seam and turbidity due to condensation of moisture in the air. Examples of such mixtures and the adhesive strengths obtained when gluing extruded acrylic glass are listed in the following table: When using nitromethane or nitroethane or their mixtures with volatile organic liquids as adhesives, the adhesive compound is manufactured by the plastic material to be bonded.

It is also possible to use so-called adhesive lacquers containing polymers dissolved in a solvent. After evaporation of the solvent, the polymer forms an adhesive compound.

The adhesives used according to the invention may contain such polymeric additions, for example polymethyl methacrylate, polyvinyl acetate, polyvinyl ether or cellulose acetobutyrate. The polymer content is limited by the viscosity of the solution. Generally, the solution viscosity at 20'C is 100
00n1pa. Must not exceed s. Advantageously, about 3 to 3 weight percent of polymer is used, which reduces the viscosity of the solution to 500
~2000rT1Pa. Set to S range. The adhesive to be used according to the invention is used first of all for gluing together parts made of methacrylic ester plastic.

This can be used with other craft materials such as wood, paper, cardboard, leather,
For bonding metals, ceramic materials, glass, porcelain or other types of plastics, such as phenolic resins, aminoblast resin moldings, polycarbonates, PVCl urethane sponges, etc., nitromethane or nitroethane alone or in combination with their volatile organic liquids can be used. Adhesive lacquers are advantageously used if the mixtures do not provide the desired adhesive strength. The mutual adhesion of parts made of acrylic glass, in particular extruded acrylic glass, is an advantageous field of use according to the invention. Acrylic glass here means cast or extruded polymethyl methacrylate or copolymers of methyl methacrylate with up to 1 weight % of other unsaturated monomers. It is advantageous for this purpose to use nitromethane or nitroethane in a mixture with dichloromethane. Table 2 already shows the use of a mixture consisting of 55 parts by weight of dichloromethane to which 4 parts by weight of nitromethane and 5 parts by weight of phenoxyethanol have been added.

These nitromethane- or monoethane-containing three-component compositions, which are variable with respect to their quantitative composition, are advantageous in their use, since they result in clear joint seams even when operated in an atmosphere of high relative humidity. It's advantageous. The same effect is achieved if, instead of phenoxyethanol, other glycol ethers are used, such as methyl glycol or alkyl diglycol ethers. To achieve high adhesive strength, these additives should be used in amounts up to 1 weight percent based on the total solvent mixture. In each of the following examples, the first bond is carried out using nitromethane and the second bond is carried out using nitroethane, otherwise under the same conditions.

When describing the tensile strength results, in each case the values obtained first with nitromethane and then with nitroethane are indicated. Example 1 Two specimen bodies (10
The long sides of the sample (2707 m x 60 m) are immersed in nitromethane or nitroethane for about 60 seconds and bonded.

The complex stabilizes within 1 second, ie it no longer displaces. Loading the joint with a weight of 150 f/d brings the adhesive surfaces into intimate contact. The load is 24J
Hold for N. After storage for 13 days at room temperature without loading,
Ten samples (8 m x 20? x 120 in order) are made from the joined body, and the tensile strength is measured according to DIN53455. Measurement results: 36.6N/i to 34.8N/I. Example 2 Example 1
Carry out gluing in the same way.

A mixture (60/40) of methylene chloride and nitromethane or nitroethane is used as solvent adhesive. The sample stabilizes during the application period. Tensile strength is 43 after 14 days of storage.
．． 7N/1d to 36. ．． 4N/WJA. Example 3
It is carried out as described in Example 1.

The mixed solvent for adhesion is methylene chloride/nitromethane or nitroethane/phenoxyethanol (55/40/
5) is used. The joint seam is completely clear and free of bubbles. After storage at room temperature for 14 days, the tensile strength is 43N/i
to 33.7N/WrlL. Example 4 The procedure is carried out analogously to that described in Example 1.

A solution of 3 parts of polymethyl methacrylate in 7 parts of a mixed solvent consisting of methylene chloride/nitromethane or nitrocotane/phenoxyethanol (57/40/3) is used. The adhesion stabilizes after 3 minutes. After storage for 14 days, the tensile strength reaches 37 N/Rd to 31.8 N/Td.

Claims (1)

[Claims] 1. A member made of methacrylic ester plastic,
By applying a liquid adhesive containing or consisting of a volatile organic solvent, bringing the parts coated with the liquid adhesive into contact with the parts to be bonded, and drying, parts made of methacrylic ester plastic can be bonded to each other or to each other. A method for adhering parts made of methacrylic ester plastic to each other or to other work materials, characterized in that the volatile organic solvent used is nitromethane, nitroethane or a mixture thereof. 2 at least 3 nitromethane and/or nitroethane
0% by weight and other volatile organic liquids with a boiling point below 200°C 7
2. A method according to claim 1, wherein an adhesive containing up to 0% by weight is used. 3. The method according to claim 2, which uses an adhesive containing nitromethane and/or nitroethane and dichloromethane in a weight ratio of 30:70 to 80:20. 4 The liquid adhesive contains a dissolved polymer and has a maximum pressure of 10,000 mPa at 20°C. The method according to any one of claims 1 to 3, wherein the liquid has a liquid viscosity of s. 5. The method according to any one of claims 1 to 4, for bonding members made of acrylic glass. 6 Based on the weight of the container mixture contained in the adhesive,
6. A method as claimed in claim 5, characterized in that adhesives containing up to 10% by weight of glycol ethers are used.