JPS6225709B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel epoxy resin composition, and more specifically, a powder epoxy resin having a sea-island structure that has low water absorption, excellent impact resistance, flexibility, and corrosion resistance, and does not lose its impact absorption ability even at low temperatures. The present invention relates to a composition. Due to its excellent performance, epoxy resins are used in applications such as paints, electricity, civil engineering and construction, and adhesives, but are particularly often used in paints. In paint applications, the demand for powder paints is gradually increasing due to the increasing need for low pollution and resource conservation in recent years. However, since the cured product lacks flexibility and impact resistance, it is susceptible to mechanical shock and thermal shock and has various limitations on its uses. In order to compensate for these shortcomings, various rubber-modified epoxy resins are being investigated, and representative examples include a butadiene low polymer containing terminal carboxyl groups and a method of improving flexibility by curing the epoxy resin. (For example, Tokukai Shou 50-3800
54-153833), a method in which a prepolymer obtained by reacting a butadiene low polymer containing a terminal hydroxyl group with an acid anhydride is used as a curing agent for an epoxy resin to improve flexibility (for example, JP-A-Sho et al. 51―
36299) or a rubber-modified epoxy resin obtained by reacting a butadiene-acrylonitrile copolymer rubber having an amino group at the molecular end with an epoxy resin (Japanese Patent Application Laid-open No. 49719/1983). In the case of these rubber-modified epoxy resins, the rubber part undergoes phase separation during heat curing and forms a sea-island structure, which gives it the ability to absorb impact energy and further alleviates internal stress during curing. . However, these methods cannot obtain a uniformly cured resin due to poor compatibility with the epoxy resin, and furthermore, it is difficult to independently control the particle size of the rubber phase when forming this sea-island structure. There was a problem. Furthermore, since the addition of terminally crosslinked rubber is expected to have a rubber reinforcing effect, it is necessary to add a relatively large amount of rubber, which satisfies impact resistance and flexibility while maintaining the good physical properties inherent to epoxy resin. It was difficult to obtain a cured product with such performance. On the other hand, ABS resin is known as a coating film with good physical properties that does not have the blocking property that is a problem with ordinary powder coatings, and it relieves internal stress by forming particles into a non-uniform coating system. , has the function of suppressing the growth of cracks that occur. However, ABS
It is well known that resins have poor coating film smoothness and are not suitable as powder coatings (Japanese Unexamined Patent Application Publication No. 1983-1999).
143263, etc.), and even if it is added to an epoxy resin and expected to have a rubber reinforcing effect, the compatibility and smoothness of the coating film are poor and it cannot be put to practical use as a powder coating. Various other epoxy compounds that impart flexibility are known, including polyalkylene glycol-based diglycidyl ethers, and 1,3-pentadiene-based compounds (for example, JP-A-52
- No. 39732) is also disclosed. When these substances are added to an epoxy resin, flexibility is improved, but heat resistance and the like are reduced, making it difficult to obtain a cured epoxy resin with highly balanced performance. The present inventors have improved the drawbacks of conventional cured epoxy resin products and the drawbacks of the known techniques, and have achieved low absorption, excellent corrosion resistance, flexibility, and impact resistance.
As a result of extensive research into a composition that satisfies impact resistance, particularly at low temperatures, and a method for producing the same, the following invention was completed. That is, the present invention provides (A) 97 to 65 parts by weight of an epoxy resin having two or more epoxy groups in the molecule and an epoxy equivalent of 400 to 2,500, and (B) a toluene-insoluble gel content of 50% or more. The base layer rubber particles are made of at least one kind selected from a polymerizable epoxy compound having an average of 0.5 or more epoxy groups and an average of 0.1 to 1.0 acryloyl groups per molecule, and a monoethylenic glycidyl ester or ether; Epoxy-modified rubber graft-modified with monomers,
The present invention relates to a novel epoxy resin composition for powder coatings having a sea-island structure and containing 3 to 35 parts by weight of rubber. The above-mentioned epoxy-modified rubber has good compatibility with epoxy resins, so if necessary, a curing agent for epoxy resins can be added to this resin composition to form a chemical bond at the interface between the rubber phase and the epoxy resin phase. Because of its presence, the strength of the cured resin is maintained in the sea-island two-phase system. Therefore, the epoxy resin composition of the present invention has improved impact resistance and flexibility. The present invention will be explained in more detail below. The epoxy resin which is the component (A) of the present invention is a conventionally known commercially available product, namely, an epoxy resin with an epoxy group.

A compound having at least two formulas in one molecule. For details on these, see, for example, Monthly Polymer Pressure Special Issue 9 "Epoxy Resin" (June 1972)
It is explained in A typical example thereof is a condensate of epichlorohydrin and a bisphenol compound. In this case, the bisphenol compound is, for example, 2,2-bis(4,
4'-Hydroxyphenyl)propane (commonly known as bisphenol A), halogenated bisphenol A, bis(4,4'-hydroxyphenyl)methane (commonly known as bisphenol F), bis(4,4'-hydroxyphenyl) ) Sulfone (commonly known as bisphenol S)
can be mentioned. Preferred is bisphenol A type glycidyl ether epoxy resin. This can also be used in combination with a novolac type epoxy resin, a hydantoin type epoxy resin, or a glycidyl ester type epoxy resin. Epoxy resin has an epoxy equivalent of 400 to 2500
A crushable solid epoxy is preferred. As such powder epoxy resin, Asahi Kasei Corporation's product name AER-664 (epoxy equivalent: 900~
1000), AER-667 (epoxy equivalent 1750-2150)
etc. can be mentioned. The base rubber particles used in component (B) have a toluene-insoluble gel content of 50% or more, and include conjugated 1,3-diene homopolymers and such 1,3-diene homopolymers used in the production of ordinary ABS resins. , 3-diene and one or more copolymerizable monoethylenically unsaturated monomers (e.g. styrene, alphamethylstyrene, chlorostyrene, acrylonitrile, methacrylonitrile, alkyl methacrylate)
Examples include co-weights with. The alkadiene content is related to elastic factors, especially the low-temperature shock absorption capacity of the coating. That is, as the secondary transition temperature increases, the temperature range in which it functions as a rubber dispersion resin becomes narrower. Appropriate.
The preferred composition of the rubber is about 75-100% by weight of alkadiene monomers and monovinylidene aromatic hydrocarbons (e.g. styrene) and unsaturated nitrites (e.g. acrylonitrile) or mixtures thereof. Approximately 0 to 25% by weight
It is. Regarding the degree of crosslinking of the base rubber particles, it is preferable that the toluene-insoluble gel content is 50% or more. If it is less than 50%, the rubber reinforcing effect will be poor, so a large amount of rubber is added to maintain the same impact resistance. Must. Note that this gel content is determined by the following method. After adding 10 g of rubber latex to 40 g of alcohol such as isopropyl alcohol, vacuum dry at room temperature. Accurately weigh 0.2 g of this dried sample, add it to 50 ml of toluene, and let it stand for 24 hours. Then, filter through a 10-mesh screen, dry at 140°C for 30 minutes, and weigh accurately. The gel content is defined as the ratio to the initially accurately weighed sample amount. The polymerizable epoxy compound used for graft modification is an aromatic compound having an average of 0.5 or more epoxy groups and an average of 0.1 to 1.0 acryloyl groups per molecule, especially aromatic epoxy resins and (meth) Preference is given to epoxy (meth)acrylates obtained by reaction with acrylic acid. As a manufacturing method, the method described in JP-A-57-105418 can be cited. The preferred amount of the polymerizable epoxy compound is 3 to 40 parts by weight based on 100 parts by weight of the rubber to be graft-modified. If the amount is less than 3 parts by weight, the compatibility with the epoxy resin will not be improved, while if it is added in an amount exceeding 40 parts by weight, there will be little polymerization residue during emulsion graft polymerization, making it difficult to produce. On the other hand, monoethylenic glycidyl esters or ethers,
For example, in the case of glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, and methacryl glycidyl ether, the amount added is 3 to 10 parts by weight. The monofunctional monomer used for graft modification is preferably an ethylenic monomer, such as methyl acrylate, ethyl acrylate, propyl acrylate,
Acrylic acid alkyl esters such as butyl acrylate and 2-ethylhexyl acrylate, methacrylic acid alkyl esters corresponding to the above alkyl esters, aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and vinyl acetate. , vinyl esters such as vinyl propionate, and unsaturated nitriles such as acrylonitrile and methacrylonitrile, either singly or in mixtures. In the present invention, the ratio of the amount of the polymerizable epoxy compound or monoethylenic glycidyl ester or ether to the ethylenic monomer can be arbitrarily selected, but it is preferable that ethylene The proportion of the monomer is 5 to 300 parts by weight. A preferred method for obtaining the epoxy-modified rubber of the present invention is to charge polybutadiene or styrene-butadiene rubber latex commonly used in the production of ABS resin into a reactor, and at a reaction temperature of 50 to 95°C, polymerizable epoxy compound or monoethylene This method involves adding an emulsifier and a polymerization initiator to a mixture of at least one type of glycidyl ester and an ethylenic monomer and carrying out emulsion polymerization. As the polymerization initiator, for example, peroxides, persulfates, azobis compounds, and redox systems in which these are combined with reducing agents can be used. After a certain reaction time, when most of the monomers are essentially no longer present in the system, the polymer latex is taken out, a suitable anti-aging agent is added, coagulated with an inorganic salt, washed with water,
After dehydration and drying, a white powdered epoxy acrylic modified rubber is obtained. The amount of the epoxy modified rubber added is preferably adjusted to 3 to 35 parts by weight based on the epoxy resin. If the amount is 3 parts by weight or less, the degree of improvement in impact absorption ability is not significant;
If it exceeds 35 parts by weight, the coating film will become soft and it will be difficult to balance the physical properties for practical use as a powder coating. In the present invention, the curing agent is not particularly limited. For example, commonly used novolac phenol resins, dicyandiamide, imidazoles, hydrazides, aromatic amines, and acid anhydrides can be used. The resin composition of the present invention contains silica, gypsum, quartz powder, calcium carbonate, kaolin, clay, mica, alumina, hydrated alumina, talc, dolomite, zircon, silicate compounds, titanium compounds, molybdenum compounds, antimony compounds, etc. filler,
Various additives such as pigments and anti-aging agents can be blended. In the coating film using the epoxy resin composition obtained by the present invention, epoxy-modified rubber particles by graft modification are uniformly dispersed, and the particle size and particle size distribution can be arbitrarily controlled by selecting the raw material rubber latex used. can do. Typically, the particle size of the graft modified rubber can range from as small as about 0.01 microns to as large as about 5.0 microns. Preferably, this will range from about 0.10 to 2.0 microns depending on the desired final physical properties for a given product;
Rubber particles used in ABS resin can be used.
Furthermore, since crosslinked rubber is used, the rubber reinforcing effect is efficiently expressed, and a small amount of addition is required compared to when uncrosslinked rubber is used. Therefore, the sea-island structure of the coating film relieves internal stress during curing and improves shock absorption ability, without sacrificing the physical properties inherent in epoxy resin. Therefore, this epoxy resin composition exhibits good flexibility, corrosion resistance, and excellent impact resistance over a wide temperature range, so it can be used in a wide range of applications such as external painting of steel pipes, coating of steel bars, electrical insulation, paints, etc. It is something that has. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is exceeded. In addition,
In the examples, unless otherwise specified, parts and percentages are by weight. Example 1 Synthesis method of polymerizable epoxy compounds (a) and (b) This was carried out according to the method described in Reference Example of JP-A-57-105418. However, by using bisphenol A type epoxy resin AER-331 with an epoxy equivalent of 190, no solvent is used, and the modification rate of the epoxy resin with methacrylic acid is 10% (equivalent ratio), compound (a), 40% Compound (equivalent ratio)
(b) was subjected to graft modification. 2 Graft modification method using a polymerizable epoxy compound Prepare the reactor with a tapping tube from 1,
Polybutadiene rubber latex UA-1001L (manufactured by Nippon Zeon Co., Ltd., solid content 51.5%, gel content 71
%) and 127 g of water were charged into a reactor, and after sufficiently purging with nitrogen, the temperature was raised to 80°C, and 2.5 g of a graft monomer tapping liquid consisting of 20 g of polymerizable epoxy compound (a), 24 g of butyl acrylate, and 25 g of methyl methacrylate was added. Add over time. On the other hand, as a catalyst system, 0.04 g of potassium persulfate, which is normally used in the production of ABS resin, and 1.0 g of an anionic emulsifier, such as Newcor F-60 (manufactured by Kao Atlas Co., Ltd.), are mixed with water.
It was dissolved in 30 g and added dropwise over 4 hours. That is, after the graft monomer tapping liquid has been added, it is added for another 1.5 hours to terminate the reaction. The graft-modified rubber latex thus obtained produced a stable emulsion with little coagulation during polymerization and had a solid content of 38.5%. This was salted out by adding aluminum sulfate, for example, by a conventional method for manufacturing ABS resin, and then washed with water, dehydrated, and dried to obtain a white powder of epoxy acrylic modified rubber. The influence of the graft modification composition was summarized in Table 1 using the same method as above using the polymerizable epoxy compound (a). 3 Manufacturing method of rubber-modified epoxy resin composition A predetermined amount of the epoxy acrylic modified rubber powder obtained in 2 was kneaded for 2 minutes with three rolls heated to 120°C, and after adding a predetermined amount of epoxy resin over 5 minutes. , to create a master batch, further kneaded for 10 minutes. Add a predetermined amount of flow control agent (e.g. Modaflow manufactured by Monsanto) and hardening agent to this masterbatch.
After dry blending AER HD-610 (manufactured by Asahi Kasei Corporation, modified dicyandiamide type), 90
After extruding with a co-kneader (manufactured by Busu Co., Ltd.) set at ℃, the mixture is pulverized with a pulverizer to obtain a powder sample for electrostatic coating. In order to study the influence of the base layer rubber, we produced styrene-butadiene rubber (tentative name) containing 10% styrene by emulsion polymerization according to the conventional method for manufacturing base layer rubber for ABS resin.
SB-10) (particle size 1300-1500 Å, solid content 50%, toluene-insoluble gel content 80%) was graft-modified in the same manner as above, and the physical properties of the coating film were evaluated. Comparative examples Comparative examples include AER-664P alone, non-grafted modified rubber UA-1001L, and UA-1001L made only of acrylic monomers that do not contain polymerizable epoxy compounds.
Graft product and product name Hiker CTBN1300×13
(Carboxyl group-terminated liquid butadiene/acrylonitrile copolymer manufactured by BF Gutudoritsu)
The mixture was used in AER-664P. In addition, hikers
CTBT1300×13 is liquid at room temperature, so 130℃
A masterbatch was produced by heating and melting AER-664P in advance, mixing it with Hiker CTBN1300 x 13, and then cooling it. The results of Examples and Comparative Examples are summarized in Table 1. The results of investigating the effect on physical properties of adding 5 to 40 parts of epoxy acrylic modified rubber to AER-664P are as follows: Examples 1, 2, 3, Comparative Examples 1, 2
Shown below. The results of examining the influence of the graft-modified composition are shown in Examples 1, 4, 5, and 6, and Comparative Example 4. In order to examine the influence of the base layer rubber, a rubber graft-modified with SB-10 was evaluated, and the results are shown in Example Shown in 7 and 8. As seen in the Examples in Table 1, it can be seen that all the coating films made of the resin compositions of the present invention are particularly excellent in high-speed tensile impact strength at low temperatures and DuPont impact strength. It can be seen that the water absorption of the graft unmodified rubber or Hiker CTBN1300×13 system is higher than that of the epoxy resin alone system, but when the graft modified rubber is used, it is significantly improved and is not much different from the epoxy resin.

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Claims (1)

[Scope of Claims] 1 (A) 97 to 65 parts by weight of an epoxy resin having two or more epoxy groups in the molecule and having an epoxy equivalent of 400 to 2,500, and (B) a toluene-insoluble gel content of 50% or more. A certain base layer rubber particle is mixed with at least one kind selected from a polymerizable epoxy compound having an average of 0.5 or more epoxy groups and an average of 0.1 to 1.0 acryloyl groups per molecule, and monoethylenic glycidyl ester or ether, and ethylene. A novel epoxy resin composition for powder coatings having a sea-island structure and containing 3 to 35 parts by weight of epoxy-modified rubber graft-modified with a synthetic monomer. 2. An epoxy compound having an average of 0.5 or more epoxy groups and an average of 0.1 to 1.0 acryloyl groups per molecule is obtained by the reaction of an aromatic epoxy resin and (meth)acrylic acid. The epoxy resin composition according to claim 1, which is an acrylate and is used in an amount of 3 to 40 parts by weight based on 100 parts by weight of the base rubber particles. 3. The epoxy resin composition according to claim 1, wherein the monoethylenic glycidyl ester is glycidyl methacrylate, and the amount used is 3 to 10 parts by weight based on 100 parts by weight of the base rubber particles.