JPS5853970A - Pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:The titled composition having improved adhesiveness and cohesive force without causing reduction in water resistance and problems of environmental hygiene, comprising a bulk material obtained by continuous bulk polymerization of an acrylic monomer a main component for adhesion. CONSTITUTION:The titled composition comprising a bulk polymer having adhesivity at normal temperature as a main component for adhesive. The bulk polymer is obtained by polymerizing quickly a polymerization raw material having a viscosity of <=10 poise at normal temperature, consisting essentially of an acrylic monomer, in the absence of a solvent which is used in a common solution polymerization, by a radical polymerization initiator in the former half zone of a transportation process, to increase the viscosity of a polymer, followed by polymerizing the polymer until it has a given conversion ratio. The polymerization is carried out in a reactor having a structure to transfer continuously successively fed contents with renewing the surface of the contents, wherein the whole zone of transportation process is controlled at a given temperature by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive adhesive composition containing an acrylic bulk polymer as the main component of the adhesive and having excellent properties.

Conventionally, solution polymerization and emulsion polymerization have been known as methods for polymerizing the polymer component of acrylic pressure-sensitive adhesive compositions, but since the former method uses a solvent, the lower the monomer a degree during polymerization, the more the solvent This makes it difficult to achieve good adhesion and cohesion, which are typical characteristics of pressure-sensitive adhesives. If such solvents are selected, problems arise in terms of toxicity and cost. On the other hand, in the latter method, it is difficult to obtain a pure product due to residual additive components such as emulsifiers, and these residual components cause problems in terms of properties such as water resistance.

In contrast, polymerization in the absence of a solvent, that is, bulk polymerization, can solve the above-mentioned problems, but this method has hitherto been considered inapplicable to acrylic polymers.

Generally, in bulk polymerization, temperature control becomes difficult due to thickening due to rapid reaction progress depending on the type of monomer, and the reaction tends to run out of control. As a result, not only is the polymerization work dangerous, but it is also difficult to design the molecular weight of the polymer, gelled products and degraded products are likely to occur as by-products, and it is difficult to obtain a homogeneous polymer (and There is a risk that this may cause problems with Canadian JL.

Among ethylenically unsaturated monomers, styrene and the like are known to be able to control relatively high conversion rates, and their bulk polymerization has been studied and industrialized for a long time. Most of the polymer is polymerized to a conversion rate of 30 to 70% in a pot-type prepolymerization vessel, and the remainder is decomposed to produce a product, or the product with the above conversion rate is fed to an extruder and gently processed. The reaction is allowed to proceed to a conversion rate of 95 to 96%.

On the other hand, acrylic monomers generate a large amount of heat during polymerization,
Even if a pot type polymerization method such as the above-mentioned styrene polymerization method is used, it is difficult to control the temperature, and the above-mentioned drawbacks due to runaway reactions cannot be avoided. For this reason, the actual situation is that industrial bulk polymerization methods for acrylic monomers have not been put to practical use.

The inventors have been conducting research on the bulk polymerization method of acrylic monomers for many years, but in the course of their research, they discovered that the large amount of heat generated during polymerization, which is an impediment to the application of the bulk polymerization method mentioned above, We investigated a method to continuously obtain homogeneous bulk polymers by taking advantage of the accompanying rapid viscosity increase.

The above method uses a reactor that can continuously transfer the contents while renewing the surface and is equipped with a temperature control function throughout the transfer process, and the acrylic monomer is fed as a living body into the reactor at room temperature. A raw material for bulk polymerization having a viscosity of 1o poise or less is continuously supplied, the viscosity is increased by rapid polymerization in the first half of the transfer process, and the bulk polymer that has reached a predetermined conversion rate as the polymerization progresses thereafter is continuously reacted. It is characterized by the fact that it can be taken out of the container, making it possible to produce bulk polymerization of acrylic monomers, which was previously considered difficult, in a continuous manner, which was not possible with other ethylene finishers.

In other words, in a reactor such as a l-screw or twin-screw extruder that can continuously transfer the contents while renewing the surface, it is extremely easy to stably transfer a substance with a constant viscosity, but if the viscosity is large in the transfer direction In the case of materials with a gradient, the transfer force of the screw etc. is not transmitted to the contents in the low viscosity region, and the transfer force is not transmitted to the contents, causing the contents to stagnate or backflow, making stable transfer difficult. It is necessary to have a state where the viscosity gradient is small. As mentioned above, acrylic monomers tend to thicken due to the rapid progress of the polymerization reaction, which has traditionally been an obstacle to the application of bulk polymerization, but the above properties are an advantage when using the above reactor. The viscosity required for stable transport can be achieved by rapid polymerization at least in the first half of the transport process. In addition, in the above method, the surface of the contents is renewed and transferred, and the contact surface between the contents and the reaction vessel is constantly renewed, so the efficiency of heat exchange between the two is good and the temperature distribution width of the contents is narrowed. Therefore, sufficient temperature control can be performed to prevent side reactions and runaway reactions from occurring.

This invention utilizes the above-mentioned continuous bulk polymerization method of acrylic polymers, and has a structure in which the continuously supplied contents are continuously transferred while renewing the surface, and throughout the entire transfer process. In a reactor heated to a predetermined temperature, a polymerization raw material containing mainly acrylic monomers and having a viscosity of 10 poise or less at room temperature is reacted with a radical polymerization initiator in the absence of a solvent used in normal solution polymerization. A pressure-sensitive adhesive whose main component is a bulk polymer that is sticky at room temperature and is obtained by increasing the viscosity by rapid polymerization in the first half of the transfer process and then proceeding with polymerization until a predetermined conversion rate is reached. This relates to a composition.

As the monomer component of the raw material used in this invention, any seven-mer component known as a polymer raw material for general acrylic pressure-sensitive adhesive compositions can be used, and usually acrylic acid or methacrylic acid and carbon number If esters with 2 to 14 alcohols or derivatives thereof are required as raw monomers, monomers that can be copolymerized with these, such as vinyl acetate, styrene, acrylonitrile, acrylic acid, methacrylic acid, (meth)acrylic acid other than the above raw monomers It is added with ester or its derivative.

The raw materials for polymerization are the above-mentioned acrylic monomers that form a polymer that is sticky at room temperature, and are generally mixed with a radical polymerization initiator and other additives such as molecular weight regulators if necessary. It is a liquid agent having a viscosity of 10 poise or less at room temperature. Examples of the above radical polymerization initiators include benzoyl peroxide, cumene hydroperoxide, and G-E.
Organic peroxides such as -butyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile can be widely used. The amount of these initiators is generally 0.01 to 100 parts by weight.
1. It's Shibe's thigh. In addition to the above-mentioned initiators, it is also possible to use redonx initiators that can generate radicals at low temperatures. As the molecular weight regulator, a chain transfer agent such as thioglycol, thioglycolic acid, butyl mercaptan, lauryl mercaptan, and decyl mercaptan is used.

In this invention, the solvent used in the above-mentioned normal solution polymerization, which is not allowed to exist in the polymerization system, is added to the raw materials before the start of the polymerization reaction for the purpose of facilitating control of the polymerization reaction, and is added to the resulting polymer. refers to inert organic solvents that are volatilized and removed when they are removed, and are collected and reused for reasons of pollution prevention and cost. Examples include benzene, toluene, ethyl acetate, heptane, hexane, methanol, ethanol, water, and mixtures thereof.

In this invention, as described above (although the above-mentioned solvent is not substantially used, it is also possible to use a monomer concentration regulator that remains in the system even after coating and drying the tape support etc.). The Zimmer modifier is added as a raw material for the purpose of increasing the amount of polymer, improving coating properties, improving compatibility, etc., and plasticizers, various resins, or bulk polymers synthesized by the method of this invention can be used.However, If a large amount of plasticizer or various resins is used, chain transfer or a decrease in the concentration of the 7-mer may occur, leading to a decrease in the polymerization rate or the molecular weight of the resulting polymer. It is desirable that the amount is 10% by weight or less.Furthermore, when the bulk polymer synthesized by the method of the present invention is used as a monomer concentration regulator, it should be used in a relatively large amount since the polymerization rate does not decrease.

Reactors that can continuously transfer the contents while renewing their surface include single- or twin-screw extruders, and the reactor of the present invention is equipped with a temperature control mechanism that covers the entire transfer process. It is.

The drawing shows a cross-sectional structure of a single screw extruder which is an example of a reactor used in the present invention, and the polymerization method will be explained below with reference to this drawing.

In the figure, reference numeral 1 denotes a barrel constituting the outer cylinder of the extruder, and one end thereof is provided with a supply port 2 for polymerization raw materials, and the other end is provided with a discharge port 3 for polymerization contents. Inside the barrel 1, a plurality of screws 5 are formed around a rotating shaft 4, and the polymerization raw materials supplied by the screws 5 are mixed and advanced by the rotation of the shaft 4. Screw 5 and barrel l
The distance between them is set appropriately to improve miscibility. Generally, about 0.5 to 2 mm is appropriate for summer. 6.7.8.9
is a heating controller installed at each part of the entire length of the barrel, and is configured to be able to control the temperature at each part to an appropriate temperature. The gas is replaced with nitrogen in advance and continuously supplied at a constant rate. The supplied raw materials are mixed by the rotation of the screw 5 and transferred while the surface is renewed. At this time, a in the diagram of the transfer process from the supply port 2 to the take-out port 3
As the viscosity increases due to rapid polymerization in the first half region shown in
For example, the temperature is controlled by the heating controller 6 so that the temperature is gradually increased in the region a2, and the temperature is controlled by the heating controller 7 so that polymerization starts instantaneously in the region a3 and the polymerization reaction proceeds rapidly.

The polymerized contents whose viscosity has increased in this way are further mixed and
The surface is renewed and transferred to the second half area, where it is heated by the heating controller 8.
, 9 to proceed with the polymerization reaction at a desired conversion rate while controlling the temperature, and finally the polymer is continuously taken out from the outlet 3 at the open end.

In this example, the axis 4 of the single-screw 5 is concentric between the screws 5, 5, but for the purpose of reaction control, each part of the barrel is configured to have a different diameter so that the polymerization raw material or polymerization contents The amount transferred may be varied.

In addition, the radical polymerization initiator and the molecular weight regulator may be added and mixed after the monomer is added alone to the reactor, instead of being mixed with the monomer from the beginning. For example, they can be introduced by providing a suitable feed port at a desired location in region a of the barrel of the illustrated l-screw extruder. 10 in the figure is a supply port provided at a portion where the axis 4 of the screw 5 on the front stage side of the region a3 is narrowed, and 11 is an exhaust port 1 of low-molecular volatiles generated by polymerization.

Furthermore, although a single screw extruder is used in the above example, polymerization can be carried out using a twin screw extruder in the same manner as above. In the case of a two-axis screw, each axis can be rotated in the same direction or in different directions. In these screw extruder models, as mentioned above, the distance between the screw and the barrel is preferably set to about 05 to 2M, and the speed gradient, i.e., pi (π)
x rotational speed female screw outer diameter/gap between barrel and screw] is generally 1,000/min or more. In addition to the above-mentioned screw extruder, the reactor used in this invention may be any reactor that can continuously transfer the contents while renewing the surface and is equipped with a temperature control mechanism over the entire transfer process. can also be used.

The bulk polymer having tackiness at room temperature obtained as described above can be used as a pressure-sensitive adhesive as it is, or it can be used as a pressure-sensitive adhesive as it is, or it can be used with tackifying resins such as rosin-modified resins, coumaron-indene resins, polyfunctional incyanates, etc. Polyfunctional epoxy, Pennzoyl peroxide.

A pressure-sensitive adhesive composition is prepared by blending various commonly used additive components such as a crosslinking agent such as carbon dioxide, fillers, and pigments. Furthermore, plasticizers such as phthalate esters and polyethers, which have already been described as being able to be added to the polymerization raw materials from the beginning, and various modifying resins can also be blended.

In addition, each of the above additive components can be added to the bulk polymer after obtaining the bulk polymer that is sticky at room temperature, or can be added at any stage of obtaining the bulk polymer, that is, at an appropriate location in the reactor. A drug supply port may be provided and the agent may be blended through the supply port.

In general, raw material polymers with low molecular weights or narrow molecular weight distributions have difficulty achieving both adhesion properties, especially tackiness and creep resistance. If the adhesive properties are increased, the adhesion properties, especially the tackiness, will be greatly reduced, and if the tackiness is emphasized, the cohesive force cannot be increased and the creep resistance will deteriorate.

The pressure-sensitive adhesive composition of the present invention has a high monomer concentration and completes polymerization in a short time, so that the rate of chain transfer to the self-polymer is higher than when other polymerization methods are used, and the molecular weight distribution is It is estimated that the polymer has a wider range of branched entanglements than those obtained by other polymerization methods, and has the advantage that it is easy to balance adhesive properties, tackiness, and creep resistance. Since it is a pure product containing no emulsifiers or dispersants, it does not have the disadvantages of a composition obtained by emulsion polymerization such as a decrease in water resistance.

Examples of the present invention will be described below, and all parts hereinafter mean parts by weight. Note that the present invention is not limited to these first embodiments, and various modifications can be made without departing from the technical idea of the present invention. In addition, measurements of adhesive strength, adhesion strength, and holding strength in Examples were performed by the following methods. The results are summarized in the table below.

(1) Adhesive strength: Measured according to JIS Z-1528.

(2) Adhesive strength; J, Dow's Rolling
Based on the Ba1l Tack measurement method.

The tapes were pasted together in an area of 110 mm x 20 mm, and a vertical load of 500 g was applied at a temperature of 40° C., and the time until the tapes fell was measured.

Example 1 Monomer mixture 1 consisting of 70 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl acrylate, and 3 parts of acrylic acid
0.00 parts of lauryl mercaptan and 0.1 part of azobisisobutyronitrile were mixed, and the mixture was sufficiently purged with nitrogen gas to obtain a raw material mixture having a viscosity of 0.7 centipoise at room temperature.

This raw material liquid was supplied at a rate of 50 Cc/min into a single screw extruder as shown in the figure, which had a screw outer diameter of 50 mm and a barrel length + l + degree gradient set to 7,850 parts.
Bulk polymerization was carried out continuously by controlling the barrel temperature within the extruder to 100°C over the entire length. The obtained bulk polymer had a polymer conversion rate of 978% and a weight average molecular weight (M
w) 440,000, number average molecular weight (Mn) 390,000, Mw/Mn
= l l, 3 was shown.

This bulk polymer was diluted with toluene, and 20 parts of rosin summer resin and 20 parts of tolylene diisocyanate were added to 2.0 parts of the raw material monomer mixture. A pressure-sensitive adhesive composition was prepared. This was applied onto a polyester film having a thickness of 50 μm using a roll coater so that the glue thickness was 50 μm, and dried at 120° C. for 3 minutes to obtain a pressure-sensitive adhesive tape.

Example 2 Monomer mixture 1 consisting of 70 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl acrylate, and 3 parts of acrylic acid
00 parts of azobisisobutyroni I-IJ was mixed with 01 parts of azobisisobutyroni I-IJ, and the mixture was sufficiently purged with nitrogen gas to obtain a raw material mixture having a viscosity of 0.6 centipoise at room temperature. Using this raw material liquid, a bulk polymerization reaction was carried out in the same manner as in Example 1, and the polymer conversion rate was 985%, and the weight average molecule it (M
w) 620,000, number average molecular weight (Mn) 4,80,000, M
w/M n = 12.9 (7) A bulk polymer was obtained.

Using this, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a pressure-sensitive adhesive tape was obtained from this.

Example 3 5 parts of dioctyl phthalate and 0.1 parts of azobisisobutyronitrile were added to 100 parts of a monomer mixture consisting of 70 parts of n-butyl acrylate, 30 parts of 2-ethyl acrylate, and 3 parts of acrylic acid. The mixture was mixed and thoroughly replaced with nitrogen gas to obtain a raw material mixture having a viscosity of 1.5 centipoise at room temperature.

This raw material mixture was polymerized in the same manner as in Example 1 to obtain a homogeneous bulk polymer with a polymer conversion rate of 956%, Mw = 420,000, Mn - 320,000, and Mw/Mn = 13.1.

Using this, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a pressure-sensitive adhesive tape was further obtained from this composition.

Example 4 The produced bulk polymer of Example 1 was added to the raw material mixture of Example 1 in an amount of 3 parts per 100 parts of the monomer mixture to produce a raw material mixture having a viscosity of 10 poise at room temperature. And so. This was polymerized in the same manner as in Example 1, and the polymer conversion rate was 9.
82%, M'w = 650,000, Mn = 5,400,000, Mw/
A homogeneous bulk polymer with Mn=12 was obtained. Using this, a pressure sensitive adhesive composition was prepared in the same manner as in Example 1,
Furthermore, a pressure-sensitive adhesive tape was obtained from this.

Example 5 01 part of lauroyl pero beef citrate was mixed with 100 parts of a monomer mixture consisting of 70 parts of n-butyl acrylate, 20 parts of 2-ethylhexyl acrylate, 10 parts of butyl acetate, and 3 parts of acrylic acid, The mixture was sufficiently replaced with nitrogen gas to obtain a raw material mixture having a viscosity of 0.8 centipoise at room temperature. Spread this mixture into a screw with an outer diameter of 40 mm and a barrel length of 1
,000mm, gap between barrel and screw crest 0.5m
50 cc was fed at a rate of 10 m into a twin screw extruder (self-cleaning type) with a stirring speed gradient set at s, ooo/min, and the barrel temperature in the extruder was kept at 10 m over the entire length.
Bulk polymerization was carried out continuously by controlling the heating to 0°C. The resulting bulk polymer had a polymer conversion rate of 968% and Mw = Using this bulk polymer, a pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, and a pressure-sensitive adhesive tape was obtained from this.

Comparative Example 1 01 parts of azobisisobutyronitrile and 300 parts of benzene were added to 100 parts of a monomer mixture consisting of 70 parts of n-butyl acrylate, 30 parts of 2-ethylhexyl acrylate, and 3 parts of acrylic acid in a three-neck flask. The dissolved oxygen was sufficiently replaced with nitrogen gas while stirring, the temperature was raised to 62°C and polymerized for 4 hours, and then the temperature was further raised to 75°C and aged for 2 hours.

The resulting polymer was directly applied onto a 50 μm thick polyester using a roll coater to give a glue thickness of 50 μm, and dried at 120° C. for 3 minutes to obtain a pressure sensitive adhesive tape. The above produced polymer was sold at a conversion rate of 43.

Comparative Example 2 The produced polymer of Comparative Example 1 was sensitized in the same manner as Comparative Example 1 by adding rosin modified resin in an amount of 20 parts and tolylene diisocyanate in an amount of 30 parts per 100 parts of the monomer mixture. It was made into a pressure adhesive tape.

Comparative Example 3 0.08 parts of lauryl mercaptan and 2 parts of a nonionic anionic emulsifier were added to 100 parts of a monomer mixture consisting of 70 parts of n-butyl acrylate, 30 parts of 2-ethyl acrylate, 30 parts of acrylic acid, and 0.08 parts of lauryl mercaptan. In addition, this was poured into a Mitsuro flask containing pure water to reduce the solid content to $1 [30
A 70% emulsion was prepared.

Next, 0.15 parts of potassium persulfate was added to 100 parts of the above monomer mixture, and after purging with nitrogen gas for about 1 hour, the temperature was raised to 70°C. A polymerization reaction was carried out for 5 hours in III, [. The obtained polymer had a conversion rate of 985%.
, Mw=490,000, Mn=12,9000, Mw/Mn=
It was 3.8.

This polymer emulsion was precipitated using a dilute hydrochloric acid-methanol system, washed, dried to form a lump, and redissolved in toluene to form a 40% solution. This polymer solution was coated onto a 50 μm thick polyester using a roll coater to form a pressure-sensitive adhesive tape.

Comparative Example 4 Using the toluene solution polymer of Comparative Example 3, the same amount of the same additive as in Comparative Example 2 was added thereto to obtain a pressure-sensitive adhesive tape.

The table below shows the measurement results of the holding force, adhesive force, and adhesive edge of each pressure-sensitive adhesive tape obtained in the above practical examples and comparative examples.

(Note) * means cohesive failure of pressure-sensitive adhesive.

From the results shown in the table above, the pressure-sensitive adhesive composition of the present invention exhibits satisfactory performance in both adhesive strength and cohesive strength, which are typical properties of pressure-sensitive adhesives, and can be obtained according to the conventional method. It can be seen that it is superior compared to the previous one.

[Brief explanation of drawings]

The drawing shows one example of a reactor used in this invention.
FIG. 2 is a cross-sectional view of a axial screw extruder.

Claims (2)

[Claims] (1) The acrylic monomer is heated in a reactor that has a structure in which the continuously supplied contents are continuously transferred while the surface is renewed, and the temperature is controlled to a predetermined 2M K throughout the entire transfer process. The polymerization raw material having a viscosity of 10 poise or less at normal temperature is thickened by rapid polymerization in the first half of the transfer process using a radical polymerization initiator in the absence of a solvent used in normal solution polymerization. A pressure-sensitive adhesive composition containing, as a main component of the adhesive, a bulk polymer obtained by proceeding with polymerization until a predetermined conversion rate is reached and which is sticky at room temperature. (2) The pressure-sensitive adhesive composition according to claim (1), which uses a l-screw or twin-screw extruder as a reactor.