JPS5848671B2 - Polyurethane material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coloring a molded article obtained by photopolymerization of an unsaturated polyurethane resin composition.

The production of molded articles using ethylenically unsaturated compounds polymerizable by the action of actinic radiation is described, for example, in V. S
．． It is well known from various publications such as No. p294661, Japanese Patent Publication No. 4319125, and Japanese Patent Publication No. 48.41708.

These are generally called photosensitive resins, and their main use is as printing plates, and they are used in conventional flexo printing.
A photosensitive resin composition is spread on a negative film, imagewise exposed, and unexposed areas are produced without the need for complicated processes or sophisticated techniques as seen in the manufacturing method of original plates for aphic printing. In other words, it became possible to make a plate by simply removing the uncured portion, and it has made many contributions to the simplification of plate-making technology and the rationalization of the process.

However, these conventional photosensitive resin molded products are usually colorless, and there has been a strong demand for colored molded products for reasons of commercial value.

However, at present, no reasonable method for coloring molded products of photosensitive resin has yet been found.

In other words, conventional methods for coloring photosensitive resins include mixing pigments into the resin stock solution, as with general synthetic resins, or coloring molded products with pigments, but the former method has a masking effect due to the presence of pigment particles. Or, sharp relief images cannot be obtained due to light reflection, refraction, etc., and the additives used in conjunction with pigments have the disadvantage of changing the performance of the cured resin, and in the latter case, the rubber elasticity of the plate material is impaired. Experiments conducted by the present inventors have revealed that each of these methods has fatal drawbacks, such as pigment peeling and non-uniformity of coating.

In addition, molded products of photosensitive resins have a 80 to 1
A method of dyeing by immersing in a dye bath at 00°C has also been tried.It requires considerable skill in adjusting the hue, density, and controlling the dyeing temperature and dyeing time, and is never satisfactory in terms of dyeing uniformity and workability. 0 The present inventors have investigated the following regarding urethane-based photosensitive resin molded products:
As a result of intensive research in order to solve the drawbacks of the conventional method and perfect a reasonably excellent coloring method, we found that by simply immersing the pre-shaped product in a specified dye solution at room temperature for a short time, it can be easily colored with excellent coloring properties. We succeeded in obtaining a reproducible coloring molded product.

That is, the method for coloring the polyurethane photosensitive resin molded product of the present invention is to apply the molded product obtained by photopolymerization reaction of an unsaturated polyurethane resin composition to an acidic saturated solution of a dye having an affinity for the polyurethane resin at a low temperature. It is characterized by being immersed in water for a short period of time.

The present invention relates to a urethane-based photosensitive resin molded product, which is the most effective and currently widely used for printing plates among many types of photosensitive resin molded products, and which has at least two or more urethane bonds in its structure. In addition, a conventionally known urethane-based photosensitive resin composition containing the necessary composition as a photosensitive resin, such as a compound having a polymerizable ethylenic double bond and a photosensitizer, is molded by a photopolymerization reaction. Refers to something that has been made into a product.

The dye used in the present invention may be any dye as long as it has an affinity for polyurethane resin.
In general, direct dyes, acid dyes (including metal complex acid dyes), disperse dyes, cationic dyes, and reactive dyes are used. Particularly favorable results can be obtained with dyes (including pattern dyes), disperse dyes, and cationic dyes.

In the present invention, the most important things when using the above dye solution are to always keep the concentration of the dye solution at a saturated concentration at the temperature and to use the dye solution in an acidic bath.

That is, in order to obtain a uniform, reproducible, and rational method for coloring polyurethane-based photosensitive resin molded products, the present inventors focused on the fact that the solubility of dyes exhibits a nearly constant amount at a certain temperature. We investigated its application and confirmed that the results were reliable. In other words, by preparing a saturated solution of the dye in advance, keeping the dye bath at a constant temperature, and immersing the molded product,
The amount of dye absorbed into the resin molded product is replenished over time by dissolving the undissolved dye present in the saturated solution, and the dye concentration in the dye bath is always maintained at the saturated concentration at that temperature. That's what it means.

When a large number of molded products are sequentially dipped and colored in the same dye bath,
In the conventional coloring method for general resin molded products, as mentioned above,
As the amount of dye in the dye bath decreases, there will be differences in hue and density between the first colored molded product and the last colored molded product, resulting in unevenly colored molded products. In order to solve this problem, it is necessary to adjust the dye concentration by adding dye to the remaining bath each time, and also to control the dye bath temperature and the immersion time of the molded product.

Since this requires considerable skill and complicated work, it is very difficult to maintain the uniformity and reproducibility of coloring of a certain molded product.

On the other hand, according to the present invention, as mentioned above, the dye concentration is always maintained in a saturated state, so the temperature of the dye bath, that is, the dye concentration in the solution part, the immersion time of the dyed object, and the dye concentration If the relationship is known for each dye, if undissolved dye is present in the dyeing system and working at the same temperature, it is possible to produce uniformly colored or molded products that are easily reproducible by simply managing the time. Obtainable.

In order to adopt such a coloring method, it is necessary to increase the ability of the dye to dye the molded product. Specifically, it is necessary to make the dye bath an acidic bath, and in order to acidify the dye bath, formic acid is used. , organic acids such as acetic acid, oxalic acid, lactic acid, citric acid, and tartaric acid, or inorganic acids such as phosphoric acid and sulfuric acid.

When selecting these acidic substances, consideration must be given to ensuring that they do not corrode the resin and that they do not cause any problems during work.

The degree of formulation of the dye bath is preferably strongly acidic with a pH of 1 to 3.
The amount added, pH, etc. are adjusted depending on the type and concentration of the dye, the composition of the dyed object, etc.

Next, in the present invention, when coloring the above-mentioned urethane resin molded product by immersing it in an acidic saturated solution of a dye that has an affinity for urethane resin, the coloring is carried out in an extremely short time and at a low dye bath temperature. The temperature of the dyeing bath is generally 5°C to 40°C, which means that it can be used as it is at room temperature, and by controlling the temperature with little temperature change, uniform coloring is easily possible.

In addition, the molded product can be sufficiently colored in a dye bath for 1 to 10 minutes, which greatly contributes to simplifying the work.

As described above, the coloring strength method for polyurethane resin molded products of the present invention is a method of coloring from a saturated solution, which was not possible with conventional coloring methods, and it simplifies the work and reproduces the coloring compared to the conventional method. Many excellent effects such as improved quality due to consistency and uniformity can be obtained.

Hereinafter, the present invention will be explained in detail with reference to Examples.

Reference Example 1 Polybrobylene glycol, toluidine diisocyanate, 2 parts of polyurethane polyurea obtained from ethylene diamine, 1 part of ethylene glycol dimethacrylate, 0.02 part of benzoin, 50 p.p. of hydroquinone.
p. m. A polyurethane photosensitive resin composition consisting of
A colorless and transparent flat plate-like product (thick Size 1mrn, area 20x20c
frL) was obtained.

Reference Example 2 The same polyurethane-based photosensitive resin composition as in Reference Example 1 was spread on a glass board covered with a 10 μm thick polyester film with a 3-inch spacer in between, and a negative image of type was printed on this. A film was applied, and light from a 270W high-pressure mercury lamp was irradiated for 20 seconds from the opposite side of the film surface.

Next, the film surface was irradiated in the same manner for 15 minutes.

After exposure, the uncured fat removing composition was removed by washing with water containing a neutral detergent, followed by washing with water and drying to obtain a colorless and transparent printing original plate.

This original plate had a base part thickness of 1 mm, a relief part height of 2 mm, and an area of 20 x 20 crrL1 and a weight of 88 g.

Example I C. 8 g of I-Acid Orange 88 (metal complex type acid dye) was added to 400 m of water containing an organic acid at 10°C.
1 to prepare a saturated dye solution.

The molded product obtained in Reference Example 1 was immersed in this dye solution, and the transmittance at 490 mμ of the colored product obtained at each treatment time was measured using a self-recording meter with the uncolored product as a control.

The results are shown in Table 1. (The lower the transmittance, the darker the color) As is clear from Table 1, due to the presence of acidic substances,
The dye can be dyed to a practical density in a short time of 3 to 5 minutes from a low-temperature dye bath at 0°C.

Example 2 15F of the same dye as in Example 1 was added to a formic acid aqueous solution of 40% of each concentration.
The dyeing property was measured in the same manner as in Example 1 after being immersed for 5 minutes at 10°C, 20°C and 30°C.

The results are shown in Table 2. Example 3 C. I. Acid Orange 8 (acid dye,
Solubility is 0.005g (approximately 30g/L) at 30℃
,0.05g,0.5g and 2.5,! 9 was put into 500 ml of 20% citric acid aqueous solution at 30°C.

Of these four concentrations of dye solutions, 2.5. ! 7/5
00rIll had undissolved dye, and the others were true solutions.

For each dye solution, 50% of the original printing plate obtained in Reference Example 2 was added.
The first coloring was carried out by dipping for a minute.

Next, the undyed original plate was immersed in each residual bath for 5 minutes and colored. O05. ! 9 for the second time, 0.05g for the fifth time, 0.5. ! For i', a difference in hue and density was observed at the 45th time from each of the first times.

However, with 2.5 g of a saturated solution, even if dyeing was repeated 80 times or more, the same hue and density as the first dyeing was obtained.

Example 4C. I-Basic Orange 2 7 (cationic dye f4) 10g and oxalic acid]. The molded product obtained in Reference Example 1 was immersed for 1.5 minutes.

When coloring a colorless molded product under the same conditions was repeated 100 times by stirring the remaining bath of Sara J, 4 of the colored products were colored.
The transmittance at 88 mμ was 17 to 19%, and the reproducibility was so excellent that the difference in hue and density could not be discerned with the naked eye.

Claims (1)

[Claims] 1. When coloring a molded product obtained by a photopolymerization reaction of an unsaturated polyurethane resin composition, the molded product is immersed for a short time at low temperature in an acidic saturated solution of a dye that has an affinity for the polyurethane resin. Coloring method for polyurethane resin molded products