JPS6291534A - Method of bonding polyoxymethylene - Google Patents

Abstract

PURPOSE:To bond polyoxymethylene firmly to each other or to other material, by treating its surface with a low-temperature plasma, brining it into contact with a compd. having a C=C bond and bonding it with an adhesive. CONSTITUTION:In bonding polyoxymethylene to each other or to other material, its surface is previously treated with a low-temperature plasma and then brought into contact with a compd. contg. a carbon-to-carbon double bond to polymerize said compd. Said plasma must be a low-temperature one. A high-temperature plasma has excessively high energy that it causes high-molecular material to be broken during treatment, so that is is impossible to treat only the surface of the polymer. When a low-temperature plasma is used, only the surface can be treated under specified conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an improved method of bonding polyoxymethylene. More specifically, the present invention relates to a method for firmly adhering polyoxymethylenes to each other or polyoxymethylene and another substance when using an adhesive.

Conventional technology Polyoxymethylene is also commonly called polyacetal resin, and because it has extremely high lllllllility, it is used as an engineering plastic in the form of injection molded products and extrusion molded products, such as automobiles, home appliances, precision machinery parts, etc. It is widely used in various fields.

Recently, polyoxymethylene has been stretched to improve its mechanical properties, and fibers have been improved. +! It is being used as a 1III material. For example, a method of stretching polyoxymethylene at a high stretching ratio, that is, a super-stretching technology, was developed.
“Industrial Materials” Volume 62, No. 4, Page 92 (198
4th year], [Poly-mar] J 2nd
Volume 6, page 426 (1985), Japanese Patent Publication No. 60-5
No. 2618], it is known that the polyoxymethylene fibers and wires obtained by this ultra-stretching method are materials with physical properties close to those of steel, exhibiting a tensile strength of about 1.5 GPa and a tensile modulus of over 40 GPa. It is being

When fibers and wire rods obtained by such super-stretching methods are used as materials such as ropes and wires, it is difficult to knot or caulk, so it is necessary to connect the ends with adhesive. It must be strong enough to withstand the load during use. 1k for many uses
l? An adhesive strength of /lllI2 or higher is required.

However, regarding adhesion of polyoxymethylene,
The same question applies to both non-oriented products such as general injection molded products and oriented products such as the wire obtained by super-stretching. Until now, no adhesive method has been found that is extremely difficult and can be put to practical use, let alone that has an adhesive strength of 1 yu/word or more.
There is a real situation.

By the way, as a method of treating polyoxymethylene with an adhesive, a method is known in which polyoxymethylene whiskers are treated with a polyurethane adhesive and used as reinforcing fibers for composite materials ( Even in this method, sufficient adhesive strength cannot be obtained.

Problems to be Solved by the Invention The purpose of the present invention is to solve the following problems when bonding polyoxymethylene to each other or to bonding polyoxymethylene to another substance using an adhesive.
An object of the present invention is to provide a bonding method capable of obtaining a large adhesive strength of 1 to 9/2 or more.

Means for Solving the Problems As a result of extensive research in order to solve the above problems, the inventors of the present invention have found that adhesive strength is improved by subjecting the surface of polyoxymethylene to a low-temperature plasma treatment in advance, and carbon-based materials such as acrylamide It was discovered that by bringing a compound having a carbon-21 bond into contact with the surface of polyoxymethylene that had been subjected to plasma treatment, the adhesive strength exceeded 1 to 9/2, and based on this knowledge, the present invention was developed. It was completed.

That is, according to the present invention, when bonding polyoxymethylene to each other or to bonding polyoxymethylene to another substance using an adhesive, the surface of the polyoxymethylene is treated with low-temperature plasma in advance to form a carbon-carbon double bond. This is a method for adhering polyoxymethylene, which is characterized by bringing a compound into contact with the surface and polymerizing the compound.

The polyoxy7-methylene used in the method of the present invention may be obtained by a known polymerization method using formaldehyde, trioxane, etc. as a raw material, or may be a copolymer obtained by copolymerizing polymers, homopolymers, ethylene oxide, etc. Furthermore, it may be non-oriented or oriented.

Examples of non-oriented polyoxymethylene include pellets,
This includes all products that do not undergo a process of applying stress such as stretching or rolling to orient the polymer, such as injection molded products and extrusion molded products.

On the other hand, polyoxymethylene-coated bodies include, for example, ultra-drawn fibers obtained by drawing undrawn fibers obtained by melt spinning, ultra-drawn wire rods obtained by drawing extruded products, or -axially or biaxially drawn fibers. There are films, etc., birefringence, wide-angle xf
This includes all methods in which the orientation of polymers can be observed by methods such as il scattering, small-angle X@ scattering, and infrared dichroism.

The method of the present invention can be applied to both cases of adhering polyoxymethylene to each other and adhesion of polyoxymethylene to other substances. It is intended for adhesion.

A plasmat is a substance in which energy leaks and dissociates into Yin and Yang charged particles, which are the constituent elements of the substance, resulting in an ionized gas, which is in a highly excited and unstable state compared to a normal gas.

A plasma in which the entire system is homogenized to a high energy state is called a high-temperature plasma, and a state in which only electrons have a high energy/I/E state, such as in a low-pressure ionized gas, is called a low-temperature plasma. To create plasma within a container, a method of applying an electric field and discharging it is used. Usually divided into DC electric field and high frequency electric field.

When the pressure of the gas sealed inside is lowered, a low-temperature plasma is generated, and current begins to flow from about 10" T+Orr, and
At around - torr, the discharge tm also increases, and excited light emission unique to the filled gas is observed. Responsible for electric discharge (・Hands are electronic,
These electrons and gas molecules collide with each other to excite or ionize gas molecules. Therefore, high-energy electrons, excited molecules or atoms, ions, radicals, etc. coexist in Pradamas.

There are two methods for generating plasma: methods that use electrodes, such as glow discharge between flat electrodes, and corona discharge between a needle-like electrode and a counter electrode, and methods that do not use electrodes. -HK
Methods using the above-mentioned electrodes are often used to treat polymers, and high-frequency discharge is common.

In the present invention, the plasma must be a so-called low-temperature plasma. High-temperature plasma requires too much energy, and with polymeric materials, the material is imaginary during processing, making it impossible to process only the surface. With low-temperature plasma, it is possible to process only the optical surface of a polymer material by selecting conditions.

Although any method may be used to generate low-temperature plasma in the present invention, glow discharge and corona discharge are preferred.

The electric field used is preferably a high frequency electric field, usually 13.5
6 MHz is used. The gas used for plasma generation is an inert gas such as alpine or helium, 0□, N2, or C.
Any reactive gas such as O2 or NH3 may be used, but
Inert gas is preferred from the viewpoint of reproducibility of treatment effects.

Figure 1 shows one of the plasma treatment equipment (glow discharge treatment equipment).
Give an example. 1 is the electrode, 2 is the sample (polyoxymethylene)
, 3 is a support stand, 4 is a true pump, 5 is a vacuum gauge, and 6 is a high frequency oscillator (13,56MHz), and the processing power, degree of vacuum, and processing time are selected as necessary to control the degree of processing to D0.
reduce

For improving adhesion, the degree of plasma treatment of polyoxymethylene that causes unevenness (etching) on the optical surface is preferable.

In the present invention, the plasma-treated polyoxymethylene is preferably brought into contact with a compound having a carbon-carbon double bond immediately after the treatment. This is because if too much time passes after the treatment, the radicals generated by the plasma treatment will disappear, and polymerization will not occur sufficiently even if the compound is brought into contact with the compound. Plasma-treated polyoxymethylene is preferably stored at low temperatures, such as liquid nitrogen temperatures.

In the present invention, a compound having a carbon-carbon double bond is a compound having a double bond such as a vinyl compound, a vinylidene compound, an olefin, a diene, etc., and which can be turned into a polymer by DO polymerization. In order to increase the affinity for , compounds with highly reactive or polar side chains are preferred, such as acrylamide, acrylic acid, styrene, vinyl chloride, and vinylidene chloride.

To bring the plasma-treated polyoxymethylene into contact with the compound, the compound, a bath solution of the compound, or an emulsion of the compound may be directly applied, or the polyoxymethylene may be immersed in the solution. The polymerization of the compound may proceed at room temperature or may require heating, and the polymerization temperature may be selected depending on the reactivity of the compound.

After the polymerization reaction is completed, it is preferable to use the adhesive after removing unreacted monomers, water and solvent from the optical surface of the polyoxymethylene.

Examples of adhesives used in the method of the present invention include thermosetting adhesives such as epoxy, phenol resin, and isocyanate adhesives, real melt adhesives such as polyester and polyamide adhesives, and rubber adhesives. Although any substance can be used, it is preferable to select an appropriate substance according to the type of compound having a carbon-carbon21 bond used.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

Note that the adhesive strength was measured according to the method shown below.

That is, an adhesive liquid is poured into a cubic paper mold, a polyoxymethylene sample is vertically placed in the liquid, and the adhesive liquid is allowed to solidify. After the adhesive hardens, the paper form is removed to obtain a sample having the shape shown in FIG. Next, try this! #+ was attached to a tensile tester as shown in Figure 3 and Figure 2, and a pullout test was performed on the polyoxymethylene sample, and the force F (kl?) required for pulling out, the polyoxymethylene sample, and the adhesive were From the contact area S (mm"), the adhesive strength A (y/*v+2) is calculated according to the formula (1).

If the polyoxymethylene wiping material has a circular cross section, from its diameter d (mm) and the contact length A (dragon) between the adhesive and the sample, according to the formula (II) A-F/πde ... (■) Calculate the adhesive strength A (7 mm2).

Example 1, Comparative Example 1 Polyoxymethylene homopolymer obtained by dielectric heating stretching method (Mukasei Kogyo Co., Ltd. Exhibition, Tenac 3010)
(Tensile strength 1.5 GPa, tensile modulus 45
GPa, outer diameter 1.3 mm) was subjected to low temperature plasma treatment.

The plasma processing equipment uses a high frequency electric field of 13.56 MHz to produce glow family 1! (Shimadzu LVC)
D-21W) t-used.

The plasma processing conditions are as follows.

The atmosphere was Argon flow i 1001d/min Processing power 200W Vacuum degree 0.2 zorr It was confirmed that the surface was etched and uneven.

Next, the plasma-treated sample was coated with acrylic 304[
i% aqueous solution for 24 hours at room temperature.

After immersion, it was confirmed by infrared absorption spectrum that acrylamide-attached IJDM coalescence was formed on the surface of the sample.

The sample after immersion was washed with water and then air-dried.

Next, an epoxy adhesive (manufactured by Chipaga Iggy Co., Ltd., Araldite Travid) is poured into a cubic paper mold together with an attached curing agent, and the acrylamide polymer is applied to the air-dried surface in this liquid. The polyoxymethylene was cured in a vertical position. The contact length at this time was 20 listens. After the cured sample was left for one hour, the paper mold was removed and the adhesive strength was measured according to a prescribed method. In addition, as a comparative example, the same adhesion test was conducted on an untreated ultrastretched sample of polyoxymethylene and a sample fixed only by plasma treatment.

The adhesion test was conducted on five samples. These results are shown in Table 1.

As can be seen from Table 1 of the first run, compared to the sample after plasma treatment,
The adhesive strength of the sample obtained by the method of the present invention was clearly increased, and the adhesive strength was 1 Y/- or more.

Example 2, Comparison ψS2 Polyoxy7 methylene homopolymer (Mukasei Kogyo Co., Ltd.)
! , Tenanku 3010) with an outer diameter of 2 obtained by extrusion molding
, 5y+m, inner diameter 1 rod (tensile strength 0-06C
) Pa, tensile modulus of elasticity 3 GPa) f Plasma treatment was performed using the same equipment as in Example 1 under the same conditions.

Using a scanning electron microscope, we confirmed that the surface of the plasma-treated sample was etched and had irregularities.

Next, this plasma-treated sample was immersed in a 60% by weight acrylamide water bath solution at room temperature for 1 hour.

After immersion, it was confirmed by infrared absorption spectrum that an adduct of acrylamide was formed on the surface of the sample.

The sample after immersion was washed with water and then air-dried.

This sample was subjected to the same adhesive test as in Example 1, and the adhesive strength was measured, and the results are shown in Part 2.

As a comparative example, the same adhesion test was conducted on untreated and plasma-treated polyoxymethylene samples to measure the adhesion strength. The results will be shown to the second group.

As can be seen from the second report, the adhesive strength of the sample prepared by the method of the present invention was clearly increased compared to the sample treated only with plasma, and the adhesive strength was 1 kg/mm'' or more.

Effects of the Invention According to the method of the present invention, the adhesive strength between polyoxymethylene and adhesive is 0.1 kl? /2 or less 2 or less Compared to 0.8 kg/mm2 in the case of only Zuma treatment, the adhesive strength has improved to more than 1.1 kg/mm2, reaching the adhesive strength of 1712 or more, which is desired in many applications.

The effect of expanding the actual surface area of polyoxymethylene through plasma treatment, combined with the effect of the affinity between the adhesive and the polymer generated using free radicals generated during plasma treatment as an initiator, further improves adhesive strength. It seems that it has been reached.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a glazma processing device. FIG. 2 is a perspective view showing the shape of a sample when measuring adhesive strength, in which reference numeral 7 indicates polyoxymethylene and 8 indicates the adhesive after solidification. FIG. 6 is a sectional view showing the sample shown in FIG. 2 mounted on a tensile tester, and FIG. 4 is an enlarged view of the sample shown in FIG. 11 is a chuck. Patent Applicant Asahi Kasei Kogyo Co., Ltd. Figure 1 Figure 3 Figure 4 Procedural Amendment (Voluntary) January 1985/- Japan Patent Office Commissioner Kuro 1) Akio Tono 16 Case Indication 1985 Patent Application No. 231045 No. 2, Name of the invention Method for adhesion of polyoxymethylene 3, Relationship with the amended person case Patent applicant: 1-2-6 Dojimahama, Kita-ku, Osaka (003) Makoto Seiko, President and Representative Director of Asahi Kasei Industries, Ltd. Section 4, "Detailed Description of the Invention" column 5 of the specification subject to amendment, Contents of the amendment Contents of the amendment (1) Specification, page 11, line 3 rA-F/SJ
Correct A=F/SJ. (2) Same, page 11, line 8 rA-F/πdNJ
Correct A=F/πdlJ. (3) Table 2 on page 15 of the same is amended as follows. Table 2 (4) Same, page 16, line 5 r0.8kg/msJ ro
, 7kg/Ryu 2”. that's all

Claims (1)

[Claims] When bonding polyoxymethylenes to each other or to other substances using an adhesive, the surface of the polyoxymethylene is treated with low-temperature plasma in advance, and a compound having a carbon-carbon double bond is brought into contact with the surface. A method for adhering polyoxymethylene, characterized by polymerizing the compound by