JPS6120532B2 - - Google Patents

Description

[Detailed description of the invention]

In recent years, with the aim of preventing pollution, preserving the environment, and saving labor, the development of solvent-free resins that can be cured by radiation energy such as light and electron beams has been actively carried out and is reaching the stage of practical use. These curable resins have excellent storage stability and harden quickly once activated by energy irradiation, etc. A typical example of this type of resin is unsaturated polyester resin. Compounds containing α,β unsaturated groups in the molecule, or compounds having a vinyl group at the end of the molecule, especially compounds having one or more acryloyl groups in the molecule, such as trimethylolpropane triacrylate, pentaerythritol triacrylate Among them, the latter has excellent self-crosslinking properties. However, this type of relatively low molecular weight polyol polyacrylate, or coesterification reaction products containing high concentrations of these as by-products during production (e.g. coesterification of trimethylolpropane, phthalic acid, and acrylic acid) (The reaction products obtained from this process contain a considerable amount of trimethylolpropane triacrylate, a by-product.) In the process of handling these products, health problems such as dermatitis may occur, and it is important to take measures to prevent them. Please keep this in mind. As a result of intensive study to solve these problems, we have reduced skin irritation to below a certain level.
Furthermore, we have obtained knowledge of a method for producing oligomers that fully retains the excellent curability that is the original feature of this type of compound, and can also produce cured products with excellent physical properties, which led us to complete the present invention. It is. The findings obtained by the present inventors are based on the analysis of the results of primary skin irritation tests conducted on various compounds having an acryloyl group. It is a method widely practiced in
Product Safety Commitments of the U.S.T. in the Code of Federal Regulations, Title
16, Section 1500.41 (The Consumer
Product Safety Commission of the USAin
the Code of Federal Regulations.Title 16.
Section 1500.41), and the primary skin irritation index used in the present invention is the primary irritation index obtained by this test method.
-Abbreviation PII-. Details of this test method are as follows. That is, use 6 or more white rabbits in a group whose hair has been sheared with clippers, and apply 0.5 ml of the sample to one spot. The rabbit is immobilized, a patch is applied to the specimen locally (on the paradorsal region of the back), and the body, including the patch, is immediately covered with an impermeable material such as rubber or cloth for 24 hours. After 24 hours, the patch is removed and the local skin reaction is scored according to Table 1. The rabbits are left undisturbed and the skin reaction is scored again 72 hours later. Apply the same amount to abraded skin as to healthy skin. Care should be taken to limit skin abrasions to exfoliation of the stratum corneum and not to extend to the dermis and cause bleeding. 24 and 72 hour determinations are also made on abraded skin. The primary skin irritation index (PII) is obtained by adding the 24- and 72-hour redness, crusting, and blistering values (total of 8 values) for healthy skin and abraded skin, and then dividing by 4. If PII is 2 or less, the primary skin irritation effect of the sample is judged to be mild, and 2.
A value between 5 and 5 is considered to be moderate, and a value of 6 or more is considered to represent strong local irritation.

[Table] As is already known to those skilled in the art, the coesterification reaction products of polybasic acid, polyhydric alcohol, and acrylic acid that were subjected to the primary skin irritation test were as follows:
Generally, it is a mixture of polyol polyacrylate which is a by-product and polyester polyacrylate having a degree of condensation of 1 or more, as shown in Table 2,
This reaction product exhibits large PII. However, surprisingly, it has been found that polyester polyacrylate with a degree of condensation of 1 or more, obtained by separating and removing polyol polyacrylate, exhibits a small PII. For example, the reaction product obtained by coesterifying phthalic acid, diethylene glycol, and acrylic acid in a molar ratio of 1:2:2 is The main component is a compound represented by the formula: a compound with a degree of condensation n of 0, that is, a polyol polyacrylate (in this case, diethylene glycol diacrylate), and a compound with a degree of condensation n of 1 or more, that is, a polyacrylate of a polyester polyol. The coesterification reaction product itself has a large PII of 5.4 as shown in (A) of Table 2. shows. On the other hand, in the polyester polyacrylate produced after the by-product diethylene glycol diacrylate is removed by preparative gel permeation chromatography (hereinafter abbreviated as GPC), the PII is 1.5. drastically reduced to. Similarly, the reaction product obtained by coesterifying tetrahydrophthalic acid, trimethylolpropane, and acrylic acid in a molar ratio of 1:2:4 has a PII of 2.7.
However, in a polyester polyacrylate with a degree of condensation of 1 or more from which by-produced trimethylolpropane triacrylate is removed, the PII decreases to 1.0 or less.

[Table] Therefore, the present inventors determined the PII of various acrylates.
I thought there might be a correlation between PII and molecular weight, and after conducting repeated tests, I learned that there is a close correlation between PII and molecular weight, although there is some variation. That is, as is clear from Table 3, when the molecular weight of acrylate is around 350, PII is
2.0, and when the molecular weight is 450 or more, PII becomes
If it is less than 1.5, the PII of most things will be less than 1.
At a molecular weight of 350, the PII reduction effect due to an increase in molecular weight becomes weaker.

【table】

[Table] Based on the above findings, the present inventor co-esterified unsaturated polybasic acid or/and aromatic polybasic acid, triol, and acrylic acid, and demonstrated a low skin irritation with a PII of 2 or less, and In order to produce oligomers with excellent properties, we obtained the basic idea that even if low molecular weight polyol polyacrylate with a molecular weight of less than 350 is produced as a by-product, it is essential to keep the amount sufficiently small. It is. The charging ratio of each raw material in the present invention is determined on the assumption that the oligomer produced by the method of the present invention is a polyester polyacrylate (model compound) having a structure represented by the following formula, When coesterifying a polybasic acid, a triol with a molecular weight of less than 250, and acrylic acid, the content of by-product triol triacrylate can be reduced by using each raw material in a quantitative ratio such that the degree of condensation n in the following formula is 2 or more. As a result, it has become possible to produce oligomers with low skin irritation. <Model compound> However, L is the residue of an unsaturated polybasic acid or/and aromatic polybasic acid (the number of carboxyl groups is 2 or more), M is the residue of a triol with a molecular weight of less than 250, and A is the residue of acrylic acid. The group n indicates the degree of condensation. In the present invention, n is a positive number of 2 or more, and the theoretical charging ratio of each raw material is {-
1+1/n} moles of acrylic acid {2-3+3/n}
molar, but for triols 10% of the theoretical amount
For acrylic acid, increase or decrease within the range of 5% of the theoretical amount or 25% of the theoretical amount.
It is possible to increase it within the range of . If the charging ratio of each raw material falls outside this range, the desired oligomer cannot be produced. In addition, there are many examples where the coesterification reaction of polybasic acid, polyhydric alcohol, and acrylic acid is described as if a single compound is obtained, but as in many other documents, Furthermore, as revealed by GPC analysis of the product, it is by no means a single compound, but generally consists of a mixture of polyol polyacrylate and polyester polyacrylate having various structures and molecular weights with different degrees of condensation. Therefore, the oligomer obtained as a product of the coesterification reaction in the present invention is actually a mixture containing a polyester polyacrylate having a degree of condensation of 1 or more as a main component and a polyol polyacrylate as a minor component. Triols preferably used in the present invention include glycerin, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, triethanolamine, and glycerin tri(ethylene glycol) ether. In addition, unsaturated polybasic acids, aromatic polybasic acids and their anhydrides include fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, muconic acid,
Preferably used are maleic acid, aconitic acid, phthalic acid, tetrahydrophthalic acid, hymic acid, endo acid, hettic acid, trimellitic acid, pyromellitic acid, and their anhydrides. The method for producing the oligomer according to the present invention includes:
For example, the following method is preferably used. That is, a polybasic acid or/and its anhydride, a molecular weight of
A raw material consisting of less than 250 triol and acrylic acid, a reaction solvent and an esterification catalyst, usually preferably serving as a dehydration entrainer, are charged and heated, and the water produced in the reaction is mixed as an azeotrope with the dehydration entrainer. Remove from system. The end point of the reaction is determined by the amount of water produced as a by-product, etc. The reaction solution is washed with an aqueous alkaline solution and water, the aqueous layer is separated, and the dehydration entrainer is removed under reduced pressure. By doing this, oligomers are obtained. In this case, in order to adjust the viscosity of the oligomer obtained as a product, the reaction solution after washing is mixed with other low-viscosity monomers and/or oligomers as a diluent, and then the dehydration entrainer is removed under reduced pressure. It is also possible to manufacture. Further, this reaction can also be carried out by a two-stage reaction method in which raw materials are supplied in portions or by a sequential reaction method in which raw materials are added sequentially. Furthermore, in addition to acrylic acid itself, the raw material acrylic acid includes lower alkyl esters of acrylic acid and acrylic acid halides, which can undergo reactions similar to esterification through transesterification and addition reactions. The derivatives of acrylic acid obtained can also be used. The heating temperature in the co-esterification reaction is 50-150℃
The temperature is preferably about 0.degree. C., and the reaction can be carried out at normal pressure, reduced pressure, or increased pressure. Preferred examples of the dehydration entrainer include n-hexane, n-bentane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, trichloroethylene, tetrachloroethylene, methylchloroform, diisopropyl ether, and the like. Further, as the esterification catalyst, common esterification catalysts such as sulfuric acid, hydrochloric acid, phosphoric acid, boron fluoride, p-toluenesulfonic acid, benzenesulfonic acid, and cationic exchange resins can be used as appropriate. This reaction is preferably carried out in the presence of a polymerization inhibitor, and hydroquinone, methoxyhydroquinone, p-benzoquinone, t-butylcatechol, phenothiazine, copper chloride and the like are preferably used as the polymerization inhibitor. All of the oligomers obtained by the present invention have been confirmed to have very little skin irritation such as skin irritation in primary skin irritation tests, and provide cured products that are fast-curing and have good physical properties. Each oligomer is synthesized at room temperature to elevated temperature in the presence of a radical polymerization initiator, or by irradiation with actinic light such as ultraviolet rays in the presence of a photoinitiator.
Alternatively, it has the property of quickly curing by irradiation with ionizing radiation, and can be used alone or in combination with other monomers, oligomers, polymers, dyes, pigments, inorganic fillers, sensitizers, peroxides, plasticizers, etc. When mixed appropriately, it is useful in the ink field, adhesives, binders, sealants, coating agents, cast molding materials, etc., and is particularly prized in the fields of ultraviolet curable coatings and electron beam curable coatings. The present invention will be specifically explained below with reference to Examples. Example 1 Using tetrahydrophthalic anhydride, trimethylolpropane and acrylic acid as raw materials, the condensation degree n=
Coesterification was carried out at a raw material charging ratio of 2. Briefly, 122 g of tetrahydrophthalic anhydride, 161 g of trimethylolpropane, 144 g of acrylic acid, 450 g of toluene, 6.5 g of para-toluenesulfonic acid and 0.1 g of phenothiazine were placed in a glass reactor of capacity 1 equipped with a stirrer, a thermometer and a water separator. I prepared it. Heating was performed while stirring and blowing air (200 c.c./min). When the internal temperature reached 107°C, the water produced in the reaction began to distill out as an azeotrope with toluene. The azeotropic mixture was cooled and separated into a toluene layer and an aqueous layer, the toluene layer was returned to the reaction system, and the aqueous layer was extracted from the system. As the reaction progressed, the internal temperature rose, and after 5 hours, the internal temperature reached 111°C and 47g of water was distilled out. The reaction solution was then cooled and washed with 195 g of a 5% aqueous sodium hydroxide solution, followed by 390 g of a 7% aqueous sodium sulfate solution. After washing, 0.18 g of methoxyhydroquinone was added to the reaction solution, and toluene was distilled off at 40-50°C and 2 mmHg, leaving a pale yellow oligomer 382 as a residue.
I got g. Toluene content was 5.76%. The actual molecular weight of the oligomer measured by GPC was 1080 in number average molecular weight (hereinafter referred to as MN) and 2760 in terms of weight average molecular weight (hereinafter referred to as MW). In addition, the peak height percentage of polyol polyacrylate such as trimethylolpropane triacrylate in this oligomer by GPC analysis (hereinafter
HI) was 6.1%. Dissolve 2 phr of benzyl or benzoin ethyl ether as a photoinitiator in this oligomer,
Cold rolled steel plate (JIS-G-3141, Bt#144 treatment)
After coating it to a thickness of 25 microns, it was dried with a hair dryer to evaporate residual toluene from manufacturing.
After drying, the oligomer was irradiated with ultraviolet light to check the curing properties of the oligomer. As an ultraviolet irradiation device, 8 cm below the lamp is 20
Ozone type 2Kw high pressure mercury lamp condensing light onto a conveyor running at m/min [Nippon Battery
Hi Cure Lamp HI-20N (input per unit arc = 80 W/cm) light condensing device] manufactured by Hi Cure Lamp HI-20N (input per unit arc = 80 W/cm) was used. Ultraviolet curability is measured by the number of times a coated plate is placed on a conveyor and exposed to ultraviolet light until the surface loses its tackiness. The adhesion and hardness of the cured coating were also investigated. Furthermore, the degree of influence of this oligomer on the skin was determined by a primary skin irritation test. These results are shown in Table 4 below, and an oligomer with low irritation and good curability was obtained. Example 2 The same raw materials as in Example 1 were used at a condensation degree of n=3.
Coesterification was carried out using the following amounts. A glass reactor with a capacity of 3 equipped with a stirrer, a cooler, and a water separator was charged with 482 g of trimethylolpropane, 389 g of acrylic acid, 1170 g of toluene, 25 g of para-toluenesulfonic acid, and 0.13 g of phenothiazine.
The mixture was heated and stirred while blowing air at a rate of 840 ml/min. When the pot temperature reached 108°C, the water produced in the reaction began to distill out as an azeotrope with toluene. 3
After an hour, the pot temperature reached 111°C and 95g of water was distilled out. Here, 410 g of tetrahydrophthalic anhydride was further added, and the mixture was continuously heated and stirred. After 5 hours, the kettle temperature reached 113°C and an additional 42g of water was distilled out. After cooling the reaction solution, add aqueous caustic soda solution with a concentration of 5%.
It was washed with 897 g, and subsequently with 1150 g of a 7% strength aqueous sodium sulfate solution. 0.57 g of methoxyhydroquinone was added to the toluene layer, and toluene was distilled off under conditions of 40-50°C and 2 mmHg to obtain 1453 g of pale yellow oligomer. The toluene content was 28.6%. The actual molecular weight of the oligomer by GPC is MN=
1210, MW=3800. Also, the HI of polyol polyacrylate such as trimethylolpropane triacrylate in this oligomer was 3.0% by GPC analysis. Furthermore, the results of the UV curability, paint film adhesion, hardness, and primary skin irritation tests of the oligomer conducted in the same manner as in Example 1 are shown in Table 4. An oligomer with the following properties was obtained. Example 3 Coesterification was carried out in the same manner as in Example 1 except that each raw material was used in an amount such that the degree of condensation n = 5, and 554 g of oligomer with a toluene content of 35.2% was obtained.
I got it. The actual molecular weight of the oligomer by GPC is MN=
1620, MW=6800. Also, the HI of polyol polyacrylate such as trimethylolpropane triacrylate in this oligomer was 2.8% by GPC analysis. Furthermore, the results of the UV curability, paint film adhesion, hardness, and primary skin irritation tests of the oligomer conducted in the same manner as in Example 1 are shown in Table 4, indicating that the oligomer has low irritation and good curability. An oligomer was obtained.

[Table] Examples 4 to 9 Using the polybasic acids, triols, and acrylic acids shown in Table 5 as raw materials, their charging ratios were adjusted to the degree of condensation n=
A coesterification reaction and various tests were carried out in the same manner as in Example 1 using an amount of 2, and oligomers having low skin irritation and good curability as shown in Table 6 were obtained.

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1 Triol with a molecular weight of less than 250 is 0.9{-1+1/n} to 1.1{-1+1/n} per mole of unsaturated polybasic acid, aromatic polybasic acid or/and their anhydride. }mol, acrylic acid is 0.95{2-3+3/n
} ~ 1.25 {2-3+3/n} moles of these raw materials are co-esterified. A method for producing a low skin irritation oligomer. However, is the number of carboxyl groups of the unsaturated polybasic acid or aromatic polybasic acid, and n is an integer of 2 or more.
is a positive number of 2 or more.