JPH10158413A - Electron beam irradiating method, cross-linking or curing method, and object irradiated with electron beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a variation in the state of cross-linking or curing of an object irradiated with an electron beam without homogeneously cross-linking or curing the object as a whole by irradiating the object with an electron beam by using a specific electron beam radiation apparatus. SOLUTION: A distribution of cross-link density, hardness, or degree of modification is formed in the thickness direction of an object by the irradiation with an electron beam. This irradiation is performed with a vacuum-tube electron beam radiation apparatus. Since this apparatus operates at a low acceleration voltage, the reachable depth of an electron beam is low, and since the acceleration voltage is easily controllable, the reachable depth of an electron beam can be easily controlled. In order to form a gradation structure or a layered structure without fail, the object is pref. thermally treated after partially cross- linked or cured in the thickness direction. The radiation voltage of the electron beam is pref. 100kV or lower in terms of controlling the reachable depth. The thickness of the object is pref. 10μm or higher.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of accelerating electrons by a voltage in a vacuum, extracting the accelerated electrons into a normal pressure atmosphere, and irradiating an object to be irradiated with an electron beam (EB). And a crosslinking or curing method using an electron beam, and an electron beam irradiation object.

[0002]

2. Description of the Related Art Electron beam irradiation has been proposed as a method for crosslinking or curing coating materials such as paints, printing inks, adhesives and adhesives applied to substrates, and other resin products. Many considerations have been made. This method is a method in which electrons are accelerated by a voltage in a vacuum, the accelerated electrons are taken out into a normal pressure atmosphere such as air, and an object is irradiated with an electron beam (EB).

The advantages of curing and crosslinking by electron beam irradiation include the following. (1) It is environmentally friendly because it does not need to contain an organic solvent as a diluent. (2) Fast curing speed (high productivity). (3) The work area for curing is smaller than that of thermal drying. (4) Heat is not applied to the base material (applicable to heat-sensitive materials). (5) Post-processing can be performed immediately (cooling, aging, etc. are unnecessary). (6) Since it is sufficient to control the electrical working conditions, it is easier to control than the temperature control at the time of thermal drying. (7) Since there is no need for an initiator and a sensitizer, a product having less impurities can be obtained (improved quality).

However, the conventional electron beam curing technology is to irradiate a high energy electron beam to uniformly crosslink and cure the entire irradiated object at a high speed. There is no idea of giving the cured state a variation.

In addition, in order to eliminate the problem that the apparatus is large and the initial investment is high, and that the reaction inhibition on the surface due to the generation of oxygen radicals is eliminated, it is necessary to perform inerting with an inert gas such as nitrogen which has a high running cost. Problem,
Further, there is a problem that shielding of the secondary electron beam is required.

Therefore, although the electron beam curing technique has been attracting attention as an energy-saving and environmentally friendly process that does not emit a solvent as described above, it cannot be said that it has been sufficiently put into practical use due to the above problems. It is difficult.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and does not uniformly crosslink or cure the entire irradiated object, but has a variation in the crosslinked or cured state. It is an object of the present invention to provide a method for irradiating an electron beam, and a method for curing or crosslinking such an electron beam, and an electron beam irradiation object. It is another object of the present invention to provide an electron beam irradiation method which does not cause problems on the apparatus and the like, a curing or crosslinking method, and an electron beam irradiation object.

[0008]

In order to solve the above-mentioned problems, the present invention firstly irradiates an object with an electron beam so that the cross-link density, hardness or hardness in the thickness direction of the object is increased. Provided is an electron beam irradiation method characterized by forming a distribution of a modification degree.

Secondly, there is provided an electron beam irradiation method characterized in that an irradiation object is irradiated with an electron beam to partially cross-link, cure or modify the irradiation object in the thickness direction. I do. Thirdly, the present invention provides an electron beam irradiation method characterized in that only the surface portion of the irradiation object is crosslinked, cured or modified in the above method.

Fourthly, there is provided an electron beam irradiation method according to any one of the above methods, wherein the irradiation voltage of the electron beam is 100 kV or less. Fifthly, there is provided the electron beam irradiation method according to any one of the above methods, wherein the thickness of the object to be irradiated is 10 μm or more.

Sixth, in any of the above methods,
The electron beam irradiation is performed by a vacuum tube type electron beam irradiation apparatus, and an electron beam irradiation method is provided.
Seventh, there is provided an electron beam irradiation method according to any one of the above methods, wherein the object to be irradiated is formed on a substrate.

Eighth, it is characterized in that a cross-link density or hardness distribution is formed by irradiating an electron beam to partially cross-link or cure the object to be irradiated in the thickness direction, followed by heat treatment. And a method for crosslinking or curing. Ninth
In addition, the present invention provides a crosslinking or curing method in which, in the above method, heat treatment is performed after crosslinking or curing only the surface portion of the irradiation object.

Tenthly, the present invention provides an electron beam irradiation object having a distribution of crosslink density, hardness or modification degree formed in a thickness direction by irradiation with an electron beam. Eleventh, an electron beam is provided which is partially crosslinked, cured or modified in the thickness direction by being irradiated with an electron beam.
Twelfthly, the present invention provides an electron beam irradiation object in which only the surface portion is crosslinked, cured or modified in any one of the above electron beam irradiation objects. 13thly, the present invention provides an electron beam irradiation material which is partially crosslinked or cured in the thickness direction by electron beam irradiation, and has a crosslink density or hardness distribution formed by a subsequent heat treatment.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. FIG. 1 is a schematic view showing an irradiation tube as an electron beam generator used in an electron beam irradiation apparatus for carrying out the present invention. The apparatus comprises a cylindrical vacuum vessel 1 made of glass or ceramic, an electron beam generating section 2 provided in the vessel 1 for taking out electrons emitted from a cathode as an electron beam and accelerating the electron beam, An electron beam emitting unit 3 provided at an end of the container 1 for emitting an electron beam;
And a pin section 4 for supplying power from a power supply section (not shown). The electron beam emitting section 3 is provided with a thin-film irradiation window 5. The irradiation window 5 of the electron beam emitting unit 3 has a function of transmitting an electron beam without transmitting a gas, and has a flat shape as shown in FIG. Then, an electron beam emitted from the irradiation window 5 is irradiated on the irradiation object arranged in the irradiation room.

That is, this device is a vacuum tube type electron beam irradiation device, and is fundamentally different from a conventional drum type electron beam irradiation device. 2. Description of the Related Art A conventional drum-type electron beam irradiation apparatus is of a type that irradiates an electron beam while constantly evacuating the inside of a drum.

An apparatus having an irradiation tube having such a configuration is as follows.
U.S. Pat. No. 5,414,267 discloses Am
Considered as a Min-EB device by erican International Technologies (AIT). In this apparatus, even at a low accelerating voltage of 100 kV or less, a decrease in the transmission power of the electron beam is small, and the electron beam can be extracted effectively. This makes it possible to cause the electron beam to act on the coating material on the base material at a low depth, thereby reducing the adverse effect on the base material and the generation amount of the secondary electron beam, resulting in a large shield. Is not necessarily required.

Further, since the energy of the electron beam is low, the inhibition of the reaction on the surface of the coating agent due to oxygen radicals can be reduced, and the necessity of inerting is reduced.

As described above, since the size of the shield can be reduced and inertia can be reduced, and the electron beam generating portion can be reduced in size due to the low acceleration voltage, the size of the electron beam irradiation apparatus can be dramatically reduced. It becomes possible, and the above-mentioned device is expected to be applied to various fields.

Further, since the above-mentioned device has a low accelerating voltage, the reaching depth of the electron beam is small, and the accelerating voltage can be easily controlled, so that the reaching depth of the electron beam can be easily controlled. It is.

This is shown in FIG. FIG. 3 shows a relationship between an electron beam reaching depth and an irradiation dose at each acceleration voltage when an electron beam is irradiated using the above apparatus. As is apparent from this figure, if the acceleration voltage is low, the electron beam works effectively at a low depth, and it is understood that the reaching depth can be controlled by the acceleration voltage.

In the present invention, attention is paid to the fact that the depth of arrival of the electron beam can be controlled in this manner, and by irradiating the irradiation object with the electron beam, the crosslinking density, hardness or modification degree in the thickness direction of the irradiation object is increased. Form a distribution.

That is, by irradiating an irradiation object with an electron beam at an accelerating voltage having a reaching depth up to a predetermined depth in the thickness direction, the portion is cross-linked, cured or modified. At a deeper position, the crosslink density, hardness, or degree of modification is lower than that of the upper portion, or the portion is not crosslinked, cured, or modified. Therefore, a distribution of crosslink density, hardness or modification degree is formed in the thickness direction. In other words,
It can also be said that the object to be irradiated is partially crosslinked, cured or modified in the thickness direction. A typical example is crosslinking, curing, or modifying only the surface portion of the irradiation target.

As described above, by forming the distribution of the crosslink density or the hardness, it is possible to apply the composition with a great variety. Specifically, it is possible to form a structure in which only the surface has a high hardness and the inside is soft, a structure in which only the surface has a low hardness, a gradation structure or a layer structure in which the crosslink density or hardness changes stepwise. In the present invention, the term “crosslinking / curing” includes graft polymerization, and “modification” refers to breaking of chemical bonds, orientation, etc. other than crosslinking and polymerization.

In order to form the gradation structure or the layer structure more reliably, after partially cross-linking or curing in the thickness direction of the irradiation object, heat treatment is performed to remove the uncross-linked or uncured portion. It is preferable to form a distribution of crosslinking density or hardness by crosslinking or curing to some extent.

The apparatus for applying the electron beam irradiation method of the present invention is not particularly limited, but the vacuum tube type as described above is preferable from the viewpoint of controllability. That is, min-
As described above, a vacuum tube type electron beam irradiation apparatus represented by EB can effectively extract an electron beam even at a low accelerating voltage, so that the electron beam can be applied with good controllability and at a low depth. Depth controllability is also high.

From the viewpoint of controllability of the reaching depth, the acceleration voltage of the electron beam is preferably 150 kV or less, and more preferably 100 kV or less. And 10
~ 70 kV is preferred. Further, in order to realize the electron beam irradiation method of the present invention at such a low acceleration voltage, the thickness of the irradiation target is preferably 10 μm or more, more preferably 10 to 300 μm, and still more preferably 10 to 100 μm.
m. Of course, the irradiation target having a thickness of less than 10 μm, that is, 1 to 9 μm, or the irradiation target having a thickness exceeding 300 μm may be used.

Irradiated objects to which the present invention can be applied include those which are formed relatively thinly on a substrate, such as printing inks, paints, adhesives and pressure-sensitive adhesives, and gradually release active ingredients such as poultices. Sustained-release materials, golf balls, and the like.

Of these, the printing ink and paint formed on the base material are formed by crosslinking or hardening only the surface portion, thereby suppressing the curing shrinkage of the portion in contact with the base material,
The effect of improving the adhesiveness to the substrate can be obtained. In the case of an adhesive or a pressure-sensitive adhesive, it can be applied to various uses by crosslinking and curing only the surface portion and keeping the inside soft and maintaining the adhesive effect.

Among these, the printing inks include ultraviolet and electron beam curable inks such as letterpress inks, offset inks, gravure inks, flexo inks, and screen inks.

Examples of the paint include resins such as acrylic resin, epoxy resin, urethane resin and polyester resin, and ultraviolet or electron beam curable paints using various photosensitive monomers.

Further, as adhesives and pressure-sensitive adhesives, vinyl polymerization type (cyanoacrylate type, diacrylate type, unsaturated polyester resin type), condensation type (phenol resin type, urea resin type, melamine resin type), polyaddition Reaction-curable (monomer, oligomer) adhesives such as molds (epoxy resin type, urethane resin type) and the like. As an application example of the adhesive, in addition to a conventional one, it can be applied to a substrate which is weak to heat, such as adhesion of a lens and adhesion of a glass sheet.

Examples of the substrate on which these are applied include metals such as stainless steel (SUS) and aluminum, and plastics such as polyethylene, polypropylene, polyethylene terephthalate and polyethylene naphthalate, regardless of whether they are treated or not.

In the printing inks, paints and adhesives as described above, various additives conventionally used can be used. Examples of various additives include pigments, dyes, stabilizers, solvents, preservatives, lubricants, activators, and the like.

As the above-mentioned sustained-release material, in addition to compresses,
Examples include artificial organs. When the present invention is applied to obtain a sustained-release material as described above, an irradiation target is irradiated with an electron beam to cure only a surface portion. Then,
The proportion of pores on the surface decreases, and the internal components gradually release. In this case, the thickness to be cured is preferably about 20 to 100 μm.

The golf ball also needs to have a hard surface portion and a soft interior from the viewpoint of repulsion. Therefore, a high-performance golf ball can be obtained by applying the present invention to increase the crosslink density of the surface portion and keep the inside in a soft state with a low crosslink density.

[0036]

Embodiments of the present invention will be described below. In the following description, “parts” and “%” are “parts by weight” and “% by weight”, respectively.

Example 1 Here, an example in which a metal paint is used as the curable coating composition will be described. This paint was prepared according to the following recipe. 35 parts of polyurethane acrylate (ANILOX M 6400 manufactured by Toa Gosei Chemical Industry Co., Ltd.) 10 parts of bisphenol A type epoxy acrylate (Evecryl EB600 manufactured by Daicel UCB) 25 parts of isoboronyl acrylate 30 parts of hydroxyethyl acrylate Rutile-type titanium oxide 100 parts (Taipe CR-95, manufactured by Ishihara Sangyo Co., Ltd.) 0.5 part of additive (BYK-358, manufactured by BYK)

These were mixed and dispersed in a sand mill for 1 hour to prepare a paint. This paint was applied to a 30-μm-thick metal plate (steel plate previously coated with an epoxy primer paint) and irradiated with an electron beam. As an irradiation device, a Min-EB device manufactured by AIT was used.
Irradiation conditions were as follows: acceleration voltage 50 kV, current value 500 μ
A, The conveyor speed was 10 m / min.

For evaluation, the coating film hardness was determined by pencil hardness, the coating film adhesion was determined by a cross-cut test, and the coating film was evaluated for scratch resistance. Using a non-woven fabric and a load of 500 g
The damaged state of the coating film after shaking was evaluated by eye. The evaluation criteria were as follows. Scratchability: (good) 5 to 1 (poor) Table 1 shows the evaluation results.

Example 2 An electron beam was applied under the same irradiation conditions as in Example 1 except that the same paint as in Example 1 was applied to a film thickness of 20 μm, and the acceleration voltage was changed to 40 kV. Example 1
The same evaluation criteria were evaluated with the same evaluation criteria. Table 1 shows the obtained results.

Embodiment 3 Here, an example relating to an adhesive sheet will be described. N-Butyl acrylate 41 parts 2-ethylhexyl acrylate 41 parts Vinyl acetate 10 parts Acrylic acid 8 parts was copolymerized in toluene, and the solvent was removed to obtain an acrylic polymer. 100 parts of the obtained copolymer was mixed with 60 parts of N-butylcarbamoyloxyethyl acrylate and 3 parts of polyethylene glycol diacrylate to obtain an electron beam-curable pressure-sensitive adhesive composition.

The obtained electron beam-curable pressure-sensitive adhesive composition was applied on a separator to a film thickness of 25 μm, irradiated with an electron beam under the same conditions as in Example 1, and then adhered to high quality paper to obtain a pressure-sensitive adhesive sheet. Was. The adhesive strength, tack and holding power of the obtained sheet were measured. Table 2 shows the obtained results. The methods for measuring the adhesive strength, tackiness, removability and unreacted amount of the unreacted single substance of the adhesive sheet are as follows.

(1) Measurement of Adhesive Force A test piece was 25 mm wide, and after 30 minutes of adhesion to a stainless steel plate, the test piece was peeled off at 180 ° at a pulling speed of 300 mm / min, and the adhesive force was measured. The measurement results were displayed in units of g / 25 mm. 1000g, depending on application
/ 25 mm was set as a practical range.

(2) Measurement of tack The width of the test piece was 25 mm, and the angle of inclination was measured by the ball rolling method.
It is indicated by the largest steel ball number that stops at 0 degrees. Although it depends on the application, if the steel ball number is 7 or more, it is determined that the steel ball is in the practical range.

(3) Re-peelability test The above-mentioned test piece was adhered to a stainless steel plate and left at 23 ° C. for 7 days, and then the re-peelability and adhesive residue on the peeled surface (stainless steel plate) were visually evaluated. did. The evaluation criteria were as follows. Removability: ：: good, Δ: partially peelable, ×: unpeelable Adhesive residue left on adherend…: no adhesive residue, Δ: partial adhesive residue, ×: adhesive residue on entire surface

(4) Measurement of the amount of unreacted simple substance A fixed amount of the pressure-sensitive adhesive composition after curing was collected from the pressure-sensitive adhesive sheet, and added to 50 ml of tetrahydrofuran.
It was left for a while. After standing, the mixture was filtered, and the filtrate was used as a sample to measure a gel permeation chromatography, and the unreacted monomer N in the cured pressure-sensitive adhesive composition was measured.
The weight (%) of -butylcarbamoyloxyethyl acrylate was determined. When the amount of the unreacted monomer in the cured pressure-sensitive adhesive composition was less than 1.0%, it was determined that the pressure-sensitive adhesive composition was within the practical range.
Table 2 shows the evaluation results.

Example 4 An adhesive composition was prepared under the same conditions as in Example 3, and an electron beam was irradiated under the same conditions as in Example 3 except that the accelerating voltage was set to 60 kV. Was evaluated.

(Comparative Example 1) A coated article was prepared under the conditions shown in Example 1 and an acceleration voltage of 200 kV, a current value of 5 mA and a curetron EBC 200 2030 manufactured by Nisshin High Voltage as an electron beam irradiation apparatus. Electron beam irradiation was performed at a conveyor speed of 20 m / min. The coating film hardness, the coating film adhesion and the coating film scratch resistance of the obtained coated product were evaluated in the same manner as in Example 1. Table 1 shows the obtained results.
Shown in

Comparative Example 2 An electron beam-curable pressure-sensitive adhesive composition was applied in the same manner as in Example 3, and a curetron EBC-200-20 manufactured by Nissin High Voltage Co., Ltd. was used as an electron beam irradiation device.
Electron beam irradiation was performed under the conditions of an acceleration voltage of 200 kV, a current value of 6 mA, and a conveyor speed of 7.5 m / min. The adhesive strength, tack and holding power of the obtained adhesive sheet were measured and evaluated according to the same criteria as in Example 3. Table 2 shows the obtained results.

Comparative Example 3 An electron beam-curable pressure-sensitive adhesive composition was applied in the same manner as in Comparative Example 2, and the same electron beam irradiation apparatus was used.
Electron beam irradiation was performed under the conditions of an acceleration voltage of 200 kV, a current value of 6 mA, and a conveyor speed of 22.5 m / min. On this occasion,
Because the conveyor speed was tripled, the irradiation dose was about 1
/ 3. Example 3 about the obtained adhesive sheet
The same items were evaluated with the same evaluation criteria. Table 2 shows the obtained results.

[0051]

[Table 1]

[0052]

[Table 2]

As apparent from Table 1, Examples 1 and 2
In each case, the coating film adhesion was good, whereas Comparative Example 1 was poor in adhesion. That is, in Examples 1 and 2, the cross-linking density distribution was provided in the thickness direction. Since the cross-linking density of the portion of the coating film in contact with the metal plate was reduced, no curing shrinkage occurred in that portion, and as a result While the film adhesion was improved, in Comparative Example 1, the coating film was cross-linked to the metal plate side (because the cross-linking density was high throughout the thickness direction), so that it was in contact with the metal plate. Curing shrinkage occurs in parts,
As a result, the adhesion deteriorated.

As is clear from Table 2, Examples 3 and 4 showed good adhesion to the stainless steel plate as the adherend, good tackiness and removability with steel balls, and good unreacted The amount of the monomer was small. From this, Example 3,
It was confirmed that the pressure-sensitive adhesive of No. 4 had a crosslink density distribution.
On the other hand, in Comparative Example 2, the adhesion to the stainless steel plate as the adherend and the tag by the steel ball were low. This indicates that the pressure-sensitive adhesive of Comparative Example 2 did not have a crosslink density distribution, and had a high crosslink density throughout the thickness direction. In Comparative Example 3, the conveyor speed was tripled and the irradiation dose was reduced to about 1/3. As a result, the crosslinking density was reduced, and the adhesive strength and the tag were improved. However, as can be seen from the large amount of unreacted monomer, the crosslink density was low in the entire thickness direction, resulting in poor removability.

[0055]

As described above, according to the present invention,
Instead of uniformly cross-linking or curing the entire irradiated object, a cross-linking density or hardness distribution is formed in the thickness direction,
Alternatively, since the resin is partially cross-linked or cured in the thickness direction, the cross-linked or cured state can be varied. In addition, the use of a vacuum tube type electron beam irradiation apparatus can solve the problems of the conventional apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an electron beam irradiation apparatus for carrying out the present invention.

FIG. 2 is a diagram showing an electron beam emitting unit of the apparatus of FIG.

FIG. 3 is a view showing a relationship between an electron beam reaching depth and an irradiation dose at each accelerating voltage when an electron beam is irradiated using a vacuum tube type electron beam irradiation apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum container 2 ... Electron beam generation part 3 ... Electron beam emission part 4 ... Pin part 5 ... Irradiation window

Claims (13)

[Claims] 1. An electron beam irradiation method comprising irradiating an object with an electron beam to form a distribution of crosslink density, hardness or modification degree in the thickness direction of the object. 2. An electron beam irradiation method comprising irradiating an object with an electron beam to partially crosslink, cure, or modify the object in a thickness direction. 3. The electron beam irradiation method according to claim 2, wherein only the surface portion of the irradiation object is crosslinked, cured or modified. 4. The electron beam irradiation method according to claim 1, wherein the irradiation voltage of the electron beam is 100 kV or less. 5. The electron beam irradiation method according to claim 1, wherein the object to be irradiated has a thickness of 10 μm or more. 6. The electron beam irradiation method according to claim 1, wherein the irradiation of the electron beam is performed by a vacuum tube type electron beam irradiation device. 7. The electron beam irradiation method according to claim 1, wherein the object to be irradiated is formed on a substrate. 8. A cross-linking density or hardness distribution is formed by irradiating an electron beam to partially cross-link or cure the object to be irradiated in the thickness direction, and then performing heat treatment. Crosslinking or curing method. 9. The cross-linking or curing method according to claim 8, wherein heat treatment is performed after cross-linking or curing only the surface portion of the irradiation object. 10. An electron beam irradiated object having a distribution of crosslink density, hardness or modification degree formed in a thickness direction by irradiation with an electron beam. 11. An electron beam irradiated material which is partially crosslinked, cured or modified in a thickness direction by being irradiated with an electron beam. 12. The electron beam irradiation object according to claim 11, wherein only the surface portion is crosslinked or cured. 13. An electron beam irradiated material which is partially cross-linked or cured in a thickness direction by electron beam irradiation, and has a cross-link density or hardness distribution formed by a subsequent heat treatment.