JPH0567839B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an iron pipe coated with a solvent-free two-component urethane elastomer composition for the purpose of wear resistance, chemical resistance, salt water resistance, and corrosion resistance. [Prior art] When iron pipes are used for transporting sludge or garbage, the pipes are worn out or corroded by objects passing through them (sludge, garbage, etc.), so their useful life is shortened. It is very short and difficult to use as is. Alloy ductile pipes containing chromium, nickel, etc. have been used to improve these drawbacks, but the drawbacks have not been significantly improved. For this reason, attempts have been made in recent years to line the inner surface of steel pipes with urethane elastomer.In this case, wear resistance is important, so lining with a thicker material is necessary, but tar urethane resin paint containing organic solvent It is difficult to obtain a thick coating film with a thickness of 1 mm or more, for example, using known anticorrosive paints such as . Furthermore, organic solvents are stipulated in the Organic Solvent Poisoning Prevention Regulations of the Industrial Safety and Health Act, and their handling poses safety and health problems. Moreover, the paint is
Generally, it has the disadvantage that it dries slowly and takes time to handle. Furthermore, organic solvents have the risk of ignition and explosion;
In addition, organic solvents are scattered into the atmosphere during the drying process and become a source of air pollution. In recent years, solvent-free two-component urethane resin paints have been developed to improve these drawbacks. In this case, the typical urethane resin composition is a two-component system of castor oil and polyisocyanate, and systems that use castor oil in combination with polyether polyol or polybutadiene diol instead of polyether are used. systems, and systems that use ε-caprolactone in combination have been developed, and each has been put into practical use (Japanese Patent Application Laid-Open Nos. 59-197466, 60-13855,
60-32857, 60-47074, 61-26675). However, all of these were designed as paints, especially corrosion-resistant paints, and because they are hard and have poor abrasion resistance, they cannot be used for sludge transportation, which is the purpose of the present invention.
It is not necessarily suitable for purposes such as garbage transportation. In order to coat a urethane elastomer with excellent abrasion resistance, it is desirable to coat it with a solvent-free two-component urethane elastomer composition generally called a cast-molded urethane elastomer composition. However, the most typical urethane resin compositions for cast urethane elastomers are polyol TDI prepolymer and 3,3'-dichloro-4, commonly abbreviated as MOCA.
It is a two-component system of 4′diaminodiphenylmethane.
MDCA is designated as a Class 2 Specified Chemical Substance under the Industrial Safety and Health Act, and is used to treat the human respiratory and digestive systems.
It is difficult to use, especially when spray painting, as it is thought that it may cause serious health problems to the urinary system, skin, etc. For this reason, a two-component system of polyether polyol or/and polyether polyol and isocyanate is considered, but since the polyol component has high hygroscopicity, it is generally easy to foam when forming a thick lining, making it difficult to form a stable lining. The drawback is that it cannot be done. In order to solve the above problems, the present invention provides an iron pipe coated with a solvent-free two-component urethane elastomer composition that has excellent wear resistance, chemical resistance, water resistance, and corrosion resistance, and is difficult to foam during lining. It is intended for the purpose of providing. [Means for Solving the Problems] The present invention provides (A) polytetramethylene glycol (PTMG)
(B) Polytetramethylene glycol (PTMG)
It is summarized as an iron pipe whose inner surface is coated to a thickness of 1 mm or more with a solvent-free two-component urethane elastomer composition whose main constituent is a polyol as an essential constituent. It is possible to provide an iron pipe that is problem-free and has a strong anti-corrosion coating that does not cause foaming. As the polyol that is a component of the (A) NCO-terminated urethane prepolymer used in the present invention, it is desirable to mainly use polytetramethylene glycol (PTMG), but it is preferable to use polytetramethylene glycol (PTMG), which is commonly used in the production of urethane compounds. Various other polyester polyols and/or polyether polyols can also be used in combination. The polyester polyols mentioned here include condensates of polyhydric alcohols and polybasic carboxylic acids, condensates of hydroxycarboxylic acids and polyhydric alcohols, etc. The polyhydric alcohols used in these include, for example, ethylene glycol. , propylene glycol, butanediol, diethylene glycol, glycerin, hexanthryl, trimethylolpropane, etc., and examples of polybasic carboxylic acids include adipic acid, glutaric acid, azelaic acid, fumaric acid, maleic acid, phthalic acid, and terephthalic acid. , dimer acid, pyromellitic acid and the like. Also useful as condensates of hydroxycarboxylic acids and polyhydric alcohols are castor oil and reaction products of castor oil and ethylene glycol and propylene glycol. Furthermore, as the polyester polyol, lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone can also be used. Polyether polyol is a product obtained by addition-polymerizing one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc. with a compound having two or more active hydrogens, and is a product obtained by addition-polymerizing one or more alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, etc. to a compound having two or more active hydrogens. Any known polyether polyol used in the production of resins can be used. In this case, examples of compounds having two or more active hydrogens include the polyhydric alcohols and polybasic carboxylic acids mentioned above, amines such as ethylenediamine and hexamethylene diamine, and alkanolamines such as ethanolamine and propanolamine. Examples include resorcinol, polyhydric phenols such as bisphenol, and castor oil. Furthermore, a low molecular weight polyhydroxy compound such as the above-mentioned polyhydric alcohol may be used in combination with these. By mainly using polytetramethylene glycol (PTMG), it is possible to obtain high physical properties that cannot be obtained with other polyether polyols, and it is possible to obtain products with excellent wear resistance. It also exhibits better water resistance than other polyether polyols. Furthermore, if polyester polyol is mainly used, there is a problem in terms of water resistance (hydrolysis resistance), but this point can also be solved by mainly using polytetramethylene glycol. The polyisocyanate compound used in the production of the NCO-terminated urethane prepolymer is a compound having two or more isocyanate groups in the molecule, and various compounds used in the production of ordinary polyurethane resins can be used, such as tolylene dichloromethane. Isocyanate, diphenylmethane diisocyanate, dianidine diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, bis(diisocyanatotolyl) phenylmethane, polymethylene polyphenyl polyisocyanate, carbodiimide-modified diphenylmethane diisocyanate, polymeric diphenylmethane diisocyanate, etc. Aromatic polyisocyanate compounds such as isophorone diisocyanate, dicyclohexylmethane diisocyanate (hydrogenated diphenylmethane diisocyanate), hexamethylene diisocyanate, xylylene diisocyanate, hydrogenated tolylene diisocyanate, isopropylidene bis(cyclohexyl isocyanate), etc. can be preferably used. It is also possible to use aliphatic or alicyclic polyisocyanate compounds. Among these, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, and/or polymeric diphenylmethane diisocyanate are particularly preferably used. Two or more types of polyisocyanate compounds used in the present invention may be used in combination. The isocyanate group-containing urethane prepolymer used in the present invention is obtained by reacting a polyhydroxyl compound and a polyisocyanate compound, but the reaction molar ratio between the polyhydroxyl compound and the polyisocyanate compound may be arbitrary as long as the isocyanate is in excess. It may be set based on conditions such as compounding ratio and reactivity, but it is preferably 1/1.1 to 1/10. If the ratio is closer to 1/1 than 1/1.1, the viscosity of the resin becomes too high and workability deteriorates. On the contrary, 1/
When the amount of isocyanate is in excess of 10, the reaction between the polyol component and the free isocyanate component approaches what is called a one-shot reaction, which tends to cause foaming during lining. The polyol (B) used in the present invention is NCO
All of the aforementioned polyhydroxyl compounds used for the production of terminal urethane prepolymers can be used. That is, one or more of the polyester polyols and polyether polyols described above can be used. Also, low molecular weight polyhydroxyl compounds such as the polyhydric alcohols mentioned above can be used as polyhydric alcohols.
It can also be used in combination as a lubricant. However, in this case as well, it is preferable to mainly use polytetramethylene glycol (PTMG) for the same reason as in the case of producing the NCO-terminated urethane prepolymer. The NCO-terminated urethane prepolymer, component (A) of the present invention, can be produced by a conventionally known method. For example, a desired product can be obtained by reacting a polyol and a diisocyanate at 80° C. for 2 to 20 hours in a nitrogen stream. What is the NCO-terminated urethane prepolymer that is the (A) component of the present invention and the polyol that is the (B) component?
It is preferable to use it so that the NCO/OH equivalent ratio is 1.3/1 to 0.9/1. If it is 1.3 or more, foaming tends to occur during lining, and if it is less than 0.9, the physical properties will deteriorate significantly. In addition to the constituent components of the urethane elastomer composition, organometallic compounds such as dibutyltin dilaurate and dibutyltin diacetate and various amines may be added as reaction catalysts, and titanium oxide, Bengara, yellow lead, and carbon black may be added as reaction catalysts. , organic or inorganic coloring pigments such as phthalocyanine blue, rust preventive pigments such as red lead, calcium leadate, zinc chromate, basic lead chromate, zinc molybdate, and condensed zinc phosphate, silica, barite, calcium carbonate, It is also possible to incorporate extender pigments such as clay, talc, and mica, and to use various smoothing agents, moisture absorbers, silanes, titanium-based coupling agents, etc. as auxiliary agents. As a coating method for iron pipes, it is also possible to coat the inner surface of the iron pipe with a urethane elastomer formed in advance to the desired thickness, but considering the adhesion between the iron pipe and the urethane elastomer, the productivity of the coated iron pipe, etc., it is difficult to coat the iron pipe. It is preferable to apply the coating to a desired thickness. The method for coating iron pipes is to treat the surface with a grinder or wire brush, and then apply the solvent-free two-component urethane elastomer composition of the present invention while rotating the pipe. The solvent-free two-component urethane elastomer composition of the present invention can be applied by pouring at room temperature or heated to 50 to 80°C, by spraying, by brushing, or by centrifugal projection. Spray painting is preferred. In order to improve painting workability and prevent damage to the paint film, it is desirable to heat the iron pipe to 60 to 90°C before painting. The film thickness can be adjusted as desired, but from the viewpoint of wear resistance, etc., it is preferable to set the film thickness to 1 mm or more. [Effects of the Invention] According to the present invention, a film thickness of 1 mm or more provides impact resistance,
Iron pipes coated with urethane elastomer having excellent chemical resistance, water resistance and corrosion resistance can be obtained. [Example] Hereinafter, the present invention will be explained with reference to Examples. (Example 1) (A) Production of NCO-terminated urethane prepolymer 100 parts of polytetramethylene glycol (PTMG) with a hydroxyl value of 56 (average molecular weight 2000) and 100 parts of diphenylmethane diisocyanate were mixed under a nitrogen gas stream.
React at 80℃ for 3 hours to produce NCO with an NCO equivalent of 286.
A terminal urethane prepolymer was obtained. (Examples 2 to 5) Polyol and isocyanate were reacted in the same manner as in Example 1 to obtain a series of NCO-terminated urethane prepolymers. Table 1 shows the components and characteristic values of each NCO-terminated urethane prepolymer. (Comparative Examples 1 to 3) Polyol and isocyanate were reacted in the same manner as in Example 1 to obtain a series of NCO-terminated urethane prepolymers. However, in Comparative Example 3, the isocyanate was used as it was. Table 1 shows the components and characteristic values of each NCO-terminated prepolymer.

【table】

[Table] Table 1 summarizes the composition and properties of the NCO-terminated urethane prepolymer, the polyol composition and properties, the elastomer coating formulation, and the results of performance tests. The resin composition and each blending amount are expressed in parts by weight. The test plates used in the performance tests were airless coated using an Asahi Ohsumi variable type two-component hot airless coater to a thickness of 4.0±0.5 mm, and then dried and cured indoors for 7 days. Note 1: Dibutyltin dilaurate is used as a catalyst to promote the reaction, and its amount was determined so that the flow time of the mixture of the base resin and curing agent would be 5 to 10 minutes. Note 2 Rubber hardness test is carried out between two glass plates.
A 12 mm thick spacer is provided, and a predetermined mixture is poured between them to create a 12 mm thick molded product.
Measured using a JIS A hardness meter. Note 3 The water supply rate test is performed by immersing a 50 x 50 x 2 mm test piece prepared in the same manner as in the rubber hardness test in tap water and calculating the weight increase before and after immersion using the following formula to determine the water absorption rate. It was displayed as . W ₀ −W/W×100 W = Weight before immersion W ₀ = Weight after immersion Note 4 The wet abrasion test was conducted using two sheets of urethane thickness 4.0 mm and cast iron thickness 6.0 mm as shown in Figure 1 A and B. A square test piece of 40 x 55 mm was made by pasting together the board pieces, and test piece 1 was placed on the bottom as shown in Figure 2 A and B.
Using a wet testing machine in which the sample was fixed with urethane rubber 2, the stirring blade 3 was rotated at a circumferential speed of 2.5 m/sec to flow the slurry 4, and the wear amount of each test piece was examined. Slurry 4 was artificial seawater containing 15% No. 3 silica sand, and was replaced with new slurry every 20 hours.

[Brief explanation of the drawing]

FIGS. 1A and 1B are a front view A and a sectional view B of a test piece subjected to a wet abrasion test, and FIGS. 2A and B are a front sectional view A and a bottom plan view B of the abrasion tester. 1... Test piece, 2... Urethane rubber, 3... Stirring blade, 4... Slurry.

Claims (1)

[Claims] 1(A) Polytetramethylene glycol (PTMG)
(B) Polytetramethylene glycol (PTMG)
An iron pipe whose inner surface is coated to a thickness of 1 mm or more with a solvent-free two-component urethane elastomer composition whose main constituent is a polyol as an essential constituent. 2. The diisocyanate used to obtain the NCO-terminated urethane prepolymer is diphenylmethane diisocyanate, or/and carbodiimide-modified diphenylmethane diisocyanate, or/and polymeric diphenylmethane diisocyanate. Iron pipe. 3. The method of claim 1, characterized in that when coating the inner surface of an iron pipe to a thickness of 1 mm or more with a solvent-free two-component urethane elastomer composition, the coating is applied by a pouring method, a spray method, a centrifugal projection method, a brush, a roller brush, etc. Iron pipe.