JPS5845268A - Heat-resistant composition for anticorrosive purpose - Google Patents

Abstract

PURPOSE:The titled composition that is made by adding a filler and a thixotropic agent to acrylic cooligomers mainly consisting of a specific unsaturated monomer, thus showing high antisagging properties at elevated temperatures, heat resistance, weather resistance and preventing the corrosion at steel pipe jointing parts in metallic structures. CONSTITUTION:The objective composition comprises (A) 100pts.wt. of acrylic cooligomers of the formula (R1 is H, methyl; R2 is 2-14C alkyl), preferably of 1,000-200,000 molecular weight and (B) 1-300pts.wt. of fillers such as calcium carbonate and/or 0.2-20pts.wt. of a thixotropic agent such as hydrogenated castor oil. USE:Nonwoven fabrics or the likes are used as a base material and the composition is used in the form of tapes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-resistant anticorrosive composition used for preventing corrosion of steel pipes, such as at joints of steel pipes.

Conventionally, anti-rust paints and plastic anti-corrosion tapes have been mainly used to prevent rust from forming on metal structures. However, in the case of anti-rust paints, the paint film shrinks and hardens over time and loses its elasticity, cracks occur in the film due to aging, and it is damaged by external impacts.
Moisture and air could easily come into contact with metal surfaces and cause rust. In addition, in the case of plastic anticorrosion tape, although it has excellent anticorrosion and antirust effects, the tape itself is quite hard, making it difficult to apply it to irregularly shaped parts such as steel pipe connections.

Therefore, attempts have been made to use a permanently adhesive plastic tape containing petrolatum as a main component for the above-mentioned irregularly shaped parts. However, for applications where this type of tape is paste-like and can be smoothed by hand, the molecular weight of the polymer must be suppressed to around several hundred, and in this case, the sagging resistance and heat resistance at high temperatures are insufficient. When the temperature exceeds the melting point of petrolatum, the paste-like substance becomes completely liquid and drips from the wrapped steel pipe, contaminating the area around the bottom, and the anti-corrosion layer on the surface of the steel pipe fades, significantly reducing its anti-corrosion properties. Ta. Moreover, if exposed to high temperatures of 130° C. or higher for a long period of time, it would carbonize and could not provide any anti-corrosion function.

In view of the above circumstances, the inventors conducted intensive studies to obtain a material that has good weather resistance as well as sagging resistance and heat resistance at high temperatures, and exhibits improved anti-corrosion performance compared to the conventional materials. As a result, they discovered that a low molecular weight acrylic copolymer is suitable for this purpose, leading to the completion of this invention.

That is, this invention is based on the following general formula; % formula % (wherein kl is hydrogen or a methyl group, k2 is
~14 alkyl groups) 1 to 30 parts by weight of filler per 100 parts by weight of an acrylic low molecular weight copolymer mainly composed of an unsaturated monomer represented by
The present invention relates to a heat-resistant anticorrosion composition containing 0 parts by weight and/or 0.2 to 20 parts by weight of a thixotropic agent.

In general, acrylic-based high molecular weight copolymers are often used as pressure-sensitive adhesives because of their excellent heat resistance and weather resistance, but their viscosity is too high and they cannot form a paste-like film. It also has poor workability when breaking in by hand, making it unsuitable for corrosion protection. However, as in the present invention, when an acrylic low molecular weight copolymer is used and a filler or thixotropic agent is used to moderate the viscosity or impart thixotropic properties, the acrylic It is possible to obtain an anti-corrosion composition that is easy to work with and is easy to work with on irregularly shaped parts without sacrificing the heat resistance and weather resistance of being a polymer. However, it was discovered that it was excellent.

As described above, the heat-resistant anticorrosion composition of the present invention can easily perform the leveling work at room temperature, can prevent dripping at high temperatures, and has excellent heat resistance and weather resistance. It is suitable for various types of corrosion protection such as steel pipe joints and other irregularly shaped parts, as well as locations with high steel pipe surface temperatures and high ambient temperatures, such as blast furnace piping and ship interior piping, which are difficult to apply with conventional petrolatum-based anticorrosion tapes. It can be widely applied.

The low molecular weight acrylic copolymer of the present invention has an unsaturated monomer represented by the above general formula as a main component, and optionally contains other unsaturated monomers copolymerizable with the above monomer. can be obtained by copolymerizing two or more of them in the presence of a polymerization initiator and a chain transfer agent.

The unsaturated monomer represented by the above general formula used here is an alkyl group (acrylic acid alkyl ester or methacrylic acid alkyl ester having 2 to 14 carbon atoms in the formula; The reason why the number of carbon atoms is limited as above is that when the number of carbon atoms is 1, that is, when it is a methyl group, the anticorrosion layer becomes hard and lacks adhesive properties, whereas when the number of carbon atoms exceeds 14, the adhesive strength to the adherend is poor. To become.

The alkyl group having 2 to 14 carbon atoms may be branched or unbranched, and specific examples include ethyl, n-butyl, isobutyl, 1-ethylpropyl, 1-ethylpropyl,
Examples include methylpentyl, 2-methylpentyl, 3-methylpentyl, 1-ethylbutyl, 2-ethylbutyl, 2-ethylhexyl, inoctyl, 3,5,5-trimethylhexyl, decyl, dodecyl, and the like.

Other unsaturated monomers that can be copolymerized with the above unsaturated monomers include alkyl (meth)acrylates other than the above general formulas, such as methyl (meth)acrylate and octadecyl (meth)acrylate. In addition, vinyl esters such as vinyl acetate, vinyl pyridine, vinyl ethers, acrylic acid, methacrylic acid, maleic acid, acrylonitrile, methacrylonitrile, methylene glutaronitrile, 2
-Hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate, N-methylolacrylamide, acrylamide, methacrylamide, glycidyl Various ethylenically unsaturated monomers such as (meth)acrylate, butadiene, cyclohexyl acrylate, β-ethoxy acrylate, sulfoacrylate, and fluoroalkyl acrylate are widely included.

The type and usage ratio of these other unsaturated monomers may be appropriately determined depending on the purpose of use of the heat-resistant anticorrosion composition, but they account for the total amount of unsaturated monomers that are the main component. If the proportion exceeds 50% by weight, heat resistance, weather resistance, durability, adhesion, etc. tend to be impaired;
It should be kept below 0% by weight.

As the polymerization initiator, any commonly used polymerization initiators can be used, such as benzoyl peroxide, lauroyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, α・α-azobisisobutyronitrile. Examples include. Normally, it can be used in a proportion of 0.05 to 2 parts by weight per 100 parts by weight of the unsaturated monomer, but if you want to control the molecular weight of the copolymer to a low value with this polymerization initiator, use a larger amount. can be used.

In addition, as a chain transfer agent, any compound having a large ability to transfer a polymer chain during polymerization may be used, and specific examples thereof include carbon tetrachloride, carbon tetrabromide, acetic acid trichloride, 2-mercaptoethanol, butyl Examples include mercaptan and lauryl mercaptan. These chain transfer agents are usually used in a ratio of 0.1 to 15 parts by weight per 100 parts by weight of the unsaturated monomer, but by changing this amount, the molecular weight of the low molecular weight copolymer can be changed. can be done. Molecular weight can also be adjusted by changing the amount of polymerization initiator, but if, for example, a large amount of polymerization initiator is used to lower the molecular weight, the heat generated by polymerization increases, making it difficult to perform polymerization operations. cause great difficulties. However,
When a chain transfer agent is used, less heat is generated and a low molecular weight copolymer can be easily produced.

Copolymerization of the unsaturated monomers may be carried out according to a conventional method, and first, a mixture of each monomer and a chain transfer agent in a predetermined ratio is charged into a polymerization tank. Regarding the charging method, you can charge the entire amount at once from the beginning of polymerization, or
Alternatively, only one portion may be added, and the remaining portion may be added gradually by a dropwise addition method as the polymerization reaction progresses. The latter method is especially advantageous for those where polymerization heat generation tends to be a problem, and in this case it is preferable to use a low molecular weight copolymer polymerized in advance on a small scale instead of fusing.

The polymerization initiator is used only after the internal temperature of the mixture of monomers and chain transfer agent reaches the predetermined polymerization temperature, and after the air in the polymerization tank has been sufficiently replaced with an inert gas such as nitrogen. It is good to add it.

In this polymerization reaction, the use of a chain transfer agent facilitates polymerization control, so a solvent as a medium is not required.
In particular, if it is desired to use a solvent, e.g. n-hebutane,
Solvents such as toluene, n-hexane, dioxane, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and isopropanol may be used.

Although the polymerization temperature varies depending on the type of monomer and polymerization initiator, a range of about 50 to 90'C is generally suitable. If the polymerization temperature becomes too high and generates too much heat, adjust it appropriately by cooling with water or the like. The polymerization time mainly depends on the above-mentioned polymerization temperature and the type of monomer. The end point of the reaction is determined so that as little unreacted monomer remains as possible and no gelation occurs, but it is usually convenient to set the end point as the point at which no heat is generated.

The acrylic low molecular weight copolymer thus obtained has an average molecular weight of about 1,000 to 200,000 and exhibits a low viscosity liquid state at room temperature. In this invention, a specific amount of filler and/or thixotropic agent is blended with a low molecular weight acrylic copolymer to obtain a heat-resistant anticorrosion composition.

The filler used here is one that moderates the viscosity of the composition and improves the workability of fitting irregularly shaped parts by hand. Examples of fillers include calcium carbonate, silica powder, talc, and magnesium silicate. , glass powder, magnesia, clay powder, titanium oxide, etc. are preferably used6.The amount thereof should be 1 to 300 parts by weight per 100 parts by weight of the acrylic low molecular weight copolymer, and less than 1 part by weight. If it is too low, the above effects cannot be obtained, and if it is too high, adhesion at room temperature will be impaired and it will be difficult to obtain desirable anticorrosion properties.

Further, the thixotropic agent used together with or in place of the filler improves the thixotropic properties of the composition, thereby improving the workability of hand smoothing like the filler, For example, hydrogenated castor oil type surfactants, polyether ester type surfactants, oxidized polyethylene type surfactants, etc. are used. The blending amount should be 0.2 to 20 parts by weight per 100 parts by weight of the acrylic low molecular weight copolymer, and within this range it should be determined depending on the viscosity of the copolymer and whether or not a filler is used in combination. The optimum blending amount is selected accordingly. If the amount is less than 0.2 parts by weight, the above effects cannot be obtained, and if it is more than 20 parts by weight, the viscosity becomes too high and the workability of hand smoothing deteriorates.

In addition to the above-mentioned components, the heat-resistant anticorrosion composition of the present invention may optionally contain a rust preventive agent such as tannic acid, a plasticizer, a pigment, an antiaging agent, a fungicide, an antioxidant, and an ultraviolet absorber. ,
Various additives such as ozone deterioration inhibitors can also be blended. In addition, when using such a composition for the purpose of anticorrosive construction, it may be impregnated into a base material such as a nonwoven fabric and used in the form of a tape or the like.

Next, examples of this invention will be described. In the following,
Part 9% indicates part by weight or weight %.

Example 1 100 parts of n-butyl acrylate, 4.3 parts of 2-hydroxyethyl acrylate and 2 parts of n-butyl mercaptan
．． 5 parts of the mixture were mixed, and 30% of this mixture was placed in a 200 cc four-necked flask and heated to 70° C. while stirring while nitrogen was being passed through the flask.

After replacing the inside of this flask with nitrogen for about 50 minutes, α・α
0.1 part of '-azobisisobutyronitrile was added. After the fever has subsided, add the remaining 70% of the above mixture.
to which 0.1 part of α·α'-azobisisobutyronitrile was added was gradually dropped into the flask using a dropping funnel over a period of 1.5 hours. Polymerization was terminated when no heat generation was observed.

The acrylic low molecular weight copolymer obtained in this way has a solid content of 99.4% (weighed after heating and drying at 150°C for 30 minutes) and a viscosity (30°C) of 95% using a B-type viscometer. The molecular weight determined by Poise and vapor pressure osmosis was 5,200. To 100 parts of this copolymer, 11 parts of calcium carbonate was added.
0 parts of tannic acid and 1 part of tannic acid were mixed together and kneaded in a planetary mixer to obtain a heat-resistant anticorrosive composition of the present invention.

Example 2 50 parts of 2-ethylhexyl acrylate, 0.25 parts of 2-hydroxyethyl methacrylate, 0.09 parts of lauryl mercaptan, and 50 parts of toluene were mixed, and the mixture was placed in a fourth flask with a capacity of 200 cc and purged with nitrogen. The mixture was heated to 70° C. while being stirred and circulated. After purging the inside of the flask with nitrogen for about 60 minutes, 0.1 part of benzoyl peroxide was added, and after the heat generation had subsided, 50 parts of 2-ethylhexyl acrylate, 0.25 part of 2-hydroxyethyl methacrylate, and lauryl were added. A mixture of 0.09 parts of mercaptan and 0.1 part of benzoyl peroxide was gradually dropped into the flask using a dropping funnel. The dropping time was 1 hour, and the polymerization was terminated when no heat generation was observed thereafter.

The acrylic low molecular weight copolymer thus obtained had a solid content of 66.1%, a molecular weight of 165.000,
The viscosity (30°C) was 980 poise. 5 parts of Disparon $305 (trade name, hydrogenated castor oil type, manufactured by Yusui Kasei Co., Ltd.) as a thixotropic agent is blended with 100 parts of the Kono copolymer, and the mixture is kneaded with a planetary mixer to produce the heat-resistant and anticorrosive product of the present invention. It was made into a composition.

Example 3 100 parts of ethyl acrylate, 6 parts of glycidyl acrylate
．． 5 parts, N-butyl mercaptan 9 parts and α・α′-
An acrylic low molecular weight copolymer was obtained according to the method of Example 1 using 0.2 parts of azobisisobutyronitrile as a polymerization raw material. This copolymer had a solid content of 99.0%, a molecular weight of 1,500, and a viscosity (30° C.) of 3,800 poise.

To 100 parts of this copolymer, 70 parts of talc, 2 parts of Disparon $3600-N as a thixotropic agent (trade name, polyether ester type surfactant, manufactured by Yusui Kasei Co., Ltd.), and 3 parts of pentaerythrityl-tetrakis. -(3-5-Gt
ert-butyl-4-hydroxyphenyl) propionate] (Product name: Irganox, manufactured by Ciba Gaiki Co., Ltd. $1
010) and kneaded in a planetary mixer to obtain a heat-resistant anticorrosive composition of the present invention.

Example 4 Using 50 parts of n-butyl acrylate, 50 parts of ethyl acrylate, 10 parts of acrylonitrile, 0.42 parts of 2-mercaptoethanol, and 0.2 parts of σ·α'-azobisisobutyronitrile as polymerization raw materials, According to the method of Example 1, an acrylic low molecular weight copolymer was obtained. The solid content of this copolymer is 99.1%, the molecular weight is 29,000, and the viscosity (
30°C) was 8,200 bois.

To 100 parts of this copolymer, 40 parts of magnesium silicate,
3 parts of finely powdered silica and 1 part of tannic acid were blended and kneaded in a planetary mixer to obtain the heat-resistant anticorrosion composition of the present invention.

Example 5 2-ethylhexyl acrylate, 5. ,,,,,Q,,
An acrylic low molecular weight copolymer was prepared according to the method of Example 1 using 50 parts of ILJ n-butyl acrylate, 3.2 parts of lauryl mercaptan, and 0.2 parts of α,α'-azobisisobutyronitrile as polymerization raw materials. Obtained union. The solid content of this copolymer is 99.4%, the molecular weight is 8,500, and the viscosity (
30°C) was 120 poise.

To 100 parts of this copolymer, 250 parts of magnesium carbonate,
1 part of Irganox $1010 (mentioned above) and 1.5 parts of tannic acid were blended and kneaded in a planetary mixer to obtain a heat-resistant anticorrosion composition of the present invention.

Example 6 100 parts of n-butyl acrylate, 10 parts of octadecyl methacrylate, 0.7 parts of lauryl mercaptan and α.
An acrylic low molecular weight copolymer was obtained according to the method of Example 1 using 0.2 part of α'-azobisisobutyronitrile as a polymerization raw material. The solids content of this copolymer is 99.3%
, molecular weight is 41,000, viscosity (3.0°C) is 5.40
It was 0 poise.

60 parts of calcium carbonate and 0.5 parts of Irganox 11010 (mentioned above) were blended with 100 parts of this copolymer and kneaded in a planetary mixer to obtain a heat-resistant anticorrosive composition of the present invention. .

The results of evaluating the characteristics of each of the compositions of Examples 1 to 6 above are as shown in the following table.

In the table, the comparative example shows the characteristics of a petrolatum-based anticorrosive composition prepared by blending 70 parts of talc and 1 part of tannic acid with 100 parts of petrolatum. Also,
The sagging resistance was evaluated as (◯) if it did not sag after being left at 150°C for 24 hours, and (x) if it sagged immediately at 150°C.

As is clear from the above table, the heat-resistant anticorrosion composition of the present invention has good sagging resistance and heat resistance, and can sufficiently exhibit anticorrosion effects. Moreover, since the heat-resistant anticorrosive composition of the present invention is mainly composed of an acrylic polymer, it is clear that it has excellent properties such as weather resistance.

Patent applicant: Nitto Electric Industry Co., Ltd. Agent: Patent attorney Moto Kunio Negi

Claims (2)

[Claims] General formula with (1); % formula % (In the formula, R+ is hydrogen or methyl group, k2 is carbon number 2
1 to 300 parts by weight of a filler and/or 0 thixotropic agent per 100 parts by weight of an acrylic low molecular weight copolymer mainly composed of an unsaturated monomer represented by 1 to 14 alkyl groups. .2 to 20 parts by weight of a heat-resistant anticorrosive composition. (2) The average molecular weight of the acrylic low molecular weight copolymer is 1,
Claim No. (1) which is from 000 to 200,000
The heat-resistant anticorrosion composition described in 1.