JPS5853973A - Production of pressure-sensitive adhesive tape - Google Patents

Abstract

PURPOSE:The continuous bulk polymerization of acrylic monomer is conducted by feeding it into a specific polymerizer to form a bulk polymer sticky at room temperature and the polymer is formed into a sheet, which is spread on a support, thus producing the titled tape through a continuous process in a short time at low costs. CONSTITUTION:A reactor that can continuously transfer the contents, while the surface is always renewed, and is provided with a temperature control mechanism all over the transferring process, preferably a single- or twine-screw extruder, is used to effect the continuous bulk polymerization by feeding a bulk polymerization mixture of less than 10 poise viscosity at room temperature, mainly consisting of acrylic monomers, e.g., the copolymerization of an ester of acrylic acid with a 2-14C alcohol, and by increasing the viscosity rapidly in the first half of the transferring zone, until the monomer conversion reaches a certain level, to make a bulk polymer that is tacky at room temperature. The resultant polymer is continuously taken out of the reactor and made into a sheet, spread on a tape support to give the objective tape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pressure-sensitive adhesive tape, and its purpose is to produce an acrylic pressure-sensitive adhesive tape with excellent properties at a low cost (and more consistently than the polymerization process of the adhesive polymer). The object of the present invention is to provide a continuous manufacturing method.

Typical methods for manufacturing pressure-sensitive adhesive tapes include applying a pressure-sensitive adhesive component diluted with water or an organic solvent onto a tape support using a roll coater and drying it, and applying a bulk pressure-sensitive adhesive using a calendar or drying method. A method of directly spreading and coating onto a tape support using a T-die or the like is known. The pressure-sensitive adhesive components used in the former method include emulsion polymers and solution polymers, but they require energy and man-hours for coating on the support and volatilizing the diluent, which is a factor in high costs. In addition to high costs, solvent-based products also pose environmental health problems and fire hazards. On the other hand, in the latter method, it is difficult to use emulsion polymers or solution polymers that have been made into lumps by some means as a bulk pressure-sensitive adhesive, which is problematic in practice. It can be said that it is most industrially advantageous to use the polymer obtained in .

However, in the bulk polymerization method, 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, it is difficult to obtain a homogeneous polymer, and This may cause the problem of knee 1-.

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 them are pot-type prepolymerizers (
Polymerize to a trowel conversion rate of 30-70% and demonomerize the remainder to produce a product, or feed the product with a double conversion rate to an extruder and perform a gentle reaction to achieve a conversion rate of 95-96%. The reaction progresses until

On the other hand, acrylic monomers have a large exothermic heat h1 during polymerization, and even if a pot type polymerization method such as styrene is used, it is difficult to control the temperature, and the above-mentioned disadvantage of runaway reaction cannot be avoided. For this reason, the actual situation is that industrial bulk polymerization methods for acrylic monomers have not yet been put to practical use.

The inventors have been researching the bulk polymerization method of acrylic monomers for many years, but in the course of their research, they discovered that the large calorific value during polymerization, which is an impediment to the application of the bulk polymerization method, as mentioned above. We have investigated a method to continuously obtain homogeneous bulk polymers by taking advantage of the rapid viscosity that accompanies this process.

The above method uses a reactor that can continuously transfer the contents while renewing the surface and is equipped with a temperature control function over the entire transfer process. A raw material for bulk polymerization having a viscosity of 10 poise or less is continuously supplied, the viscosity is increased by rapid polymerization in the first half of the transfer process, and the mass □゛5-shaped polymer that has reached a predetermined conversion rate in the subsequent polymerization progress is produced. It is characterized by being continuously taken out of the reactor, 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 ethylenic monomers.

In other words, for example, in a reactor that can continuously transfer the contents while renewing the surface, such as a single or twin screw extruder, it is extremely easy to stably transfer something with a certain precision, but if there is a large amount in the transfer direction. In the case of materials with a viscosity gradient, the transfer force of the screw, etc. in the low viscosity region becomes idle, causing accumulation or backflow of the contents, making stable transfer difficult. It is necessary to maintain a state in which the viscosity gradient is small for as long as possible.As mentioned above, acrylic monomers tend to thicken due to the rapid progress of the polymerization reaction (this has traditionally been an obstacle to the application of bulk polymerization). However, in the case of hospital use of the above-mentioned reactor, the above-mentioned properties are an advantage, and rapid polymerization can be achieved at least in the first half of the transfer process, thereby achieving the viscosity necessary for stable transfer. In this method, the contents are transferred while the surface is renewed, and the contact surface between the contents and the reactor wall is constantly renewed, so the efficiency of heat exchange between the two is good and the temperature distribution width of the contents is narrowed. Sufficient temperature control can be performed to prevent side reactions and runaway reactions.

This invention involves obtaining a bulk polymer that is sticky at room temperature by the above-described continuous bulk polymerization method of acrylic monomers, continuously molding this into a sheet shape, and coating this molded product on a tape support. The present invention relates to a method for manufacturing a pressure-sensitive adhesive tape that includes a continuous process of applying the adhesive polymer, and allows the production of a pressure-sensitive adhesive tape with excellent properties and appearance in a continuous process that is more consistent than the production of an adhesive polymer.

In this invention, monomer components of the polymerization raw material that is continuously fed to the reactor to obtain a bulk polymer having adhesiveness at room temperature include any of the monomer components that are conventionally known as raw materials for acrylic pressure-sensitive adhesives. In general, esters of acrylic acid or methacrylic acid with alcohols having 2 to 14 carbon atoms or derivatives thereof may be used as raw monomers, and monomers copolymerizable therewith, such as vinylopestylene acetate; acrylic acid, methacrylic acid, acrylonitrile. , a (meth)acrylic acid ester or a derivative thereof other than the above-mentioned raw monomers is added.

The polymerization raw material is a monomer mainly composed of the above-mentioned acrylic monomer, which can make the formed polymer sticky at room temperature, and is usually mixed with a radical polymerization catalyst and other additives such as a molecular weight regulator. It is a liquid agent that has a viscosity of 10 poise or less at room temperature.

Examples of the radical polymerization catalysts mentioned above include benzoyl peroxide, cumene dropperoxide, and
Organic peroxides such as -butyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronyl-IJ can be widely used. The amount of these catalysts is generally 0.01 parts by weight of monomer.
~1 part by weight is professional. Furthermore, in addition to the catalyst described in "2" above, it is also possible to use a redox catalyst 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 addition, in this invention, a small amount of solvent is used, if desired, in order to impart appropriate properties to the produced bulk polymer.

Plasticizers, polymers, etc. may be blended into the raw materials. The total amount of these components is desirably 25 parts by weight or less per 100 parts by weight of the monomer.

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, ■ is a barrel constituting the outer cylinder of the extruder, and one end thereof is provided with a supply port 2 for the polymerization raw material, and the other end is provided with a discharge port 3 for the polymerization contents. Inside the barrel, 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 1
The distance between them is set appropriately to improve miscibility. Generally, about 0.5 to 2M is appropriate. 6,7,8,9
10 is a heating controller provided 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, but it is of course possible to have a configuration in which the heating is controlled uniformly over the entire length.

The raw material for bulk polymerization mainly consisting of acrylic monomers is continuously fed into this extruder from the feed port 2 at a constant rate, preferably after being replaced with nitrogen in advance. The supplied raw materials are mixed by the rotation of the screw 5 and transferred while the surface is renewed. At this time, the temperature is gradually increased in the region a1 using the heating controller 6, for example, so that the viscosity increases due to rapid market increase in the first half region indicated by a in the figure during the transfer process from the supply port 2 to the take-out port 3. The temperature is controlled by the heating controller 7 so that polymerization starts instantaneously in area a2 and the polymerization reaction rapidly proceeds.

The polymer content whose viscosity has increased by -1 in this way is further mixed and surface renewed while being transferred to the second half area via the area a3 having the heating controller 8, while being temperature controlled by the heating controller 9 and lO. The polymerization reaction is allowed to proceed until the desired conversion rate is reached, and finally the polymer is continuously taken out from the takeout port 3 at the open end.

In this example, the shaft center 4 of the single-screw 5 is concentric between the screws 5, 5, but for the purpose of reaction control, the diameter is different in each part of the barrel so that the polymerization raw material or polymerization contents The amount of transport may be varied.

Further, the radical polymerization catalyst 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 suitable feed ports at desired locations within region 1 of the barrel of the illustrated l-screw extruder. Reference numeral 11 in the figure is a supply port provided in the part where the axis 4 of the screw 5 on the front stage side of area a2 is narrowed, and 12 is a supply port provided in the part where the axis 4 of the screw 5 on the front stage side of region a2 is narrowed. It is an exhaust port for molecular volatiles. 13 is a supply port for additives, which will be described later.

Further, although a single screw extruder is used in the example in item 1, polymerization can be carried out using a twin screw extruder in the same manner as described above. In the case of a two-axis screw lJ:L-, each axis can be rotated in the same direction or in different directions. In these screw extruders (G), as mentioned above, the distance between the screw and the normal part is preferably 0.5~
It is set to about 21g1, but its velocity gradient, that is, [
Generally, the ratio of "pi (pi) x rotation speed (screw outer diameter)/gap between barrel and screw" is preferably 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 that is sticky at room temperature obtained as described above is continuously formed into a sheet after being taken out of the reactor, and then sent as a bulk pressure-sensitive adhesive to a coating machine directly connected to the reactor. The tape is then deposited onto the tape support.

(11) In this case, for example, as shown by 13 in the figure, desired components such as tackifier-1 plasticizer, pigment, filler, etc. are supplied from a supply port provided at an appropriate location in the latter half of the transfer process of the reactor. If necessary, it can be continuously blended into the bulk polymer before being taken out. A crosslinking agent can also be added depending on the conditions.

Pressure-sensitive adhesives are generally heat resistant, oil resistant, and weather resistant.

Crosslinked to improve water resistance etc. In this case, with conventional pressure-sensitive adhesives diluted with water or organic solvents, various water-soluble or oil-soluble chemical crosslinking agents can be used with sufficient adjustment time due to the dilution effect, but in the case of bulk adhesives as in the present invention, With pressure-sensitive adhesives, even a slight crosslinking reaction causes problems in film-forming properties. However, by appropriately selecting the temperature conditions during extrusion and further heating after forming into a sheet, it becomes possible to use a crosslinking agent.

Examples of crosslinking agents that can be used include melamine-based agents such as ethyl etherified methylol melamine and butyl etherified methylol melamine, 121 isocyanate-based agents such as tolylene diisocyanate and hexamethylene diisocyanate, penzoylpa-oxide, di-L-
Examples include peroxides such as butyl peroxide, and epoxys such as diglycidyl ether of bisphenol A. In addition, instead of these, anthraquinone, β-methylanthraquinone, 2-methyl-1
・4-naphthoquinone, quinone dioxime, 4-benzoquinone, benzanthrone, benzophenone, and other ingredients that exhibit triplet sensitization by absorbing ultraviolet rays are blended to produce a wavelength of approximately 2,800 to 4,0 OOA after sheet forming. It is also possible to carry out photocrosslinking using ultraviolet rays emitted from a low-pressure to ultra-high-pressure mercury lamp, xenon lamp, carbon arc lamp, or the like. The above-mentioned crosslinking agent or sensitizer is used in an amount of 0.1 to 0.5 parts by weight based on 100 parts by weight of the bulk polymer.

The suitable coating machine is determined by the viscosity of the pressure-sensitive adhesive; for low-viscosity pressure-sensitive adhesives, a roll coater is recommended.
However, since the adhesive of the present invention is bulky and has a high viscosity, T-dies and calenders used in general plastic molding machines are suitable.

One of the features of the method of this invention is that the reactor for producing the pressure-sensitive adhesive and the coating machine are directly connected, and the produced bulk polymer can be directly led to the coating machine. When the polymer is taken out of the reactor, it is softened by the heat of reaction and is easily molded, so there is no need for additional man-hours or energy for molding. On the other hand, ordinary adhesives require many man-hours, energy, labor, and time, such as forming them into ribbons or pellets, and heating them to improve moldability.

The pressure-sensitive adhesive tape finally obtained can be determined by changing the composition of the bulk pressure-sensitive adhesive and the type of tape support as appropriate.

As described above, the method of the present invention enables the production of a pressure-sensitive adhesive tape using a pressure-sensitive adhesive mainly composed of an acrylic polymer in a short time, at low cost, and easily through a continuous process that is more consistent than the production of the adhesive. It has an industrial feature that allows it to be used.

Hereinafter, this invention will be specifically illustrated by Examples.

In addition, all parts in the examples mean parts by weight,
Moreover, adhesive strength and holding strength were measured by the following method.

<Adhesive Strength> Based on JISZ-1528f, 180 degree peeling adhesive strength (9,/20 n) was measured.

Holding force> A pressure-sensitive adhesive tape with a size of 25 x 25 mrt was attached to a Bakelite plate, a load of 1 Kli' was applied at 40°C, and the time (minutes) until it fell was measured.

Example 1 Screw outer diameter 40mm, barrel length 1,250wn.

A from the front end side with the gap ITML between the barrel and the screw thread
, B, C, D, E can be controlled independently 5
A single-screw extruder is used, which is divided into zones and has a supply port at the front end of zones A, D, and the temperature of each zone is set to A, 'B, C, I), F, = 100'.
C, 100°C, 100°C, 30°C, 30°C, and the speed gradient between the screw top and the barrel was set to 6,2807 minutes.

90 parts of 2-ethylhexyl acrylate and 1 liter of ethyl acrylate were added from the supply port of zone A of this reactor.

part, 2.5 parts of acrylic acid and azobisisobutyroni)
A mixed solution containing 0.15 parts of IJ and having a viscosity of 0.8 centipoise at room temperature was supplied at a rate of 40 g/min while purging with nitrogen gas to carry out a continuous bulk polymerization reaction, and at the same time, the mixture was supplied to the D zone. 55% of an 8=2 dilution of dioctyl phthalate and butyl etherified methylolmelamine by mouth.
'/min. The butyl etherified melamine was supplied in a feed ratio of 2.5 parts per 100 parts of polymer.

The bulk polymerization is continuously taken out from the above reactor, passed through a die at a temperature of 30°C, and applied to a 25 μm thick polyester film by adjusting the take-up speed so that the glue becomes 25 μm thick. , and then passed through an oven at 130° C. for 90 seconds to complete the crosslinking reaction. The pressure-sensitive adhesive tape thus obtained has an adhesive cuff 20
The retention strength was 1,000 minutes or more.

Example 2 Using the same reactor as in Example 1, the temperature of each zone of A, B, C, D, and H was 80°C; 80°C, 100°C, and 100°C.

The conditions were the same except that the temperature was set at 120°C. A mixture of 100 parts of 2-ethylhexyl acrylate, 3 parts of vinyl acetate 40J acrylic acid, and 0.15 parts of azobisisobutyronitrile was supplied from the supply port of the A zone of this reactor at room temperature in advance with nitrogen gas purging. A pressure sensitive adhesive tape was prepared according to Example 11, except that the mixture having a viscosity of 0.6 centipoise was fed at a rate of 70 V/min and the die temperature was 75°C. This tape has an adhesive strength of 850 F.
/min, and the holding power was 295 minutes.

Example 3 Two screws with outer diameter of 50 rtvn, bar zlushi,
250, it is divided into 5 zones A, B, C, I), and E whose temperature can be controlled independently from the front end side with one gap between the barrel and the screw thread. A twin-screw extruder with one feed port is used, and the temperature of each zone is set to A, B, C, D,
E=80℃, 80℃, 100℃, 100'C, 100℃
and the velocity gradient between the screw mountain and the barrel is 15.7.
00 parts g.

A mixture of 90 parts of n-butyl acrylate, 10 parts of methyl methacrylate, 1.5 parts of 2-hydroxyethyl acrylate, and 0.2 parts of azobisisobutyronitrile was added to the feed port of the A zone of this reactor at room temperature. A mixed solution having a viscosity of 0.9 centipoise is supplied at a rate of 100 V/min to carry out a continuous bulk polymerization reaction, and a mixture of dioctyl phthalate:β-methylanthraquinone-100:1 is supplied from the supply port of the D zone. The dispersion was fed at a rate of 202 parts.

The bulk polymerized product continuously taken out from the reactor was passed through a die directly connected to the reactor with a lip of 40 rrtn, a gap of 0.2, and a temperature of 75°C, and placed on a 30 μm thick semi-rigid PVC sheet. The coating was applied by adjusting the take-up speed to 5, and the surface was irradiated with ultraviolet rays from a distance of 10 cm for 3 minutes using a 400 W high-pressure mercury lamp with a wavelength of 2,800 A to cause crosslinking. The tape thus obtained had an adhesive strength of 95051'/20 and a retention cuff of 50 minutes.

[Brief explanation of the drawing]

The drawing is a sectional view of a single screw extruder which is an example of a reactor used in the present invention.

Claims (2)

[Claims] (1) A reactor is used that is capable of continuously transferring the contents while renewing the surface and is equipped with a temperature control mechanism throughout the entire transfer process, and the acrylic monomer is fed into the reactor at room temperature. A bulk polymerization raw material having a viscosity of less than 1O voids is continuously supplied, the viscosity is increased by rapid polymerization in the first half of the transfer process, and the polymerization progresses to a predetermined conversion rate in the subsequent transfer process so that it becomes sticky at room temperature. A method for producing a pressure-sensitive adhesive tape, which comprises a continuous process of forming a bulk polymer, continuously taking it out from a reactor, forming it into a sheet, and applying the formed product on a tape support. (2) The method for producing a pressure-sensitive adhesive tape according to claim (1), wherein the reactor is a l-screw or twin-screw extruder.