JPS6172075A - Quick adhesive - Google Patents

Abstract

PURPOSE:To provide the titled adhesive composed of a synthetic resin emulsion having dilatancy, having excellent initial adhesivity and mechanical properties, and suitable for a high-speed paper-bonding machine. CONSTITUTION:The objective adhesive can be prepared by imparting dilatancy preferably to an aqueous emulsion of vinyl acetate copolymer or an aqueous emulsion of vinyl acetate copolymer by properly selecting the polymerization condition and/or the composition of the resin.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a high-speed adhesive used for bonding articles at high speed, and in particular to a high-speed adhesive used for high-speed paper bonding machines. It is related to.

(Prior Art) Aqueous emulsions of homo- or copolymers of vinyl acetate are mainly used as high-speed adhesives, especially paper adhesives. This water-based emulsion adhesive does not cause environmental pollution or fire problems like solvent-based adhesives, but because the water in the emulsion dries at a low rate, initial adhesive strength is slow to develop, and mechanical aptitude, especially fluidity, is poor. Due to this inadequacy, there are various problems that must be solved when used in modern high speed bonding machines.

In general, initial adhesion and mechanical suitability are important in high-speed mechanical bonding. Initial adhesion mainly depends on the rate of viscosity increase as water evaporates and wet tack increases, and the rate of film formation as emulsion particles begin to fuse and form a film, and these depend on the type and amount of protective colloid used. It also varies depending on the emulsion concentration, as well as the type and amount of additives such as plasticizers and solvents added. On the other hand, mechanical suitability, that is, properties of adhesives required when used in high-speed bonding machines include, for example, viscosity, flow characteristics, stability, non-foaming properties, and rust prevention properties. As described above, there are many factors that influence the performance of high-speed adhesives, and each factor is interrelated, so various theories of adhesion suitability have been proposed, but none are perfect. Currently, optimal conditions are found based on experiments.

To date, various compositions have been developed and put into practical use as high-speed adhesives, but adhesives with higher-speed adhesive properties are required to increase production rates. Particularly, tobacco chip paper attachments are required to have a linear speed of 4,000 pieces per minute or more, that is, a linear velocity of about 10 m/min or more. However, conventional adhesives cannot satisfy this one performance requirement. In other words, in high-speed adhesive machines such as those mentioned above, the number of rotations of the applicator roll is extremely high, and the shearing force applied to the adhesive is extremely high, but the viscosity of conventional emulsilane-type adhesives decreases under high shearing forces. , so-called tack does not develop, initial adhesive strength is insufficient, and roll workability is poor. Furthermore, as the paper to be bonded has become thinner and has greater air permeability, in order to develop initial adhesive strength, the water in Emulsicon is allowed to penetrate into the paper and other objects to be bonded, and the polymer particles are fused together. There are limits to the drying method.

The present inventor discovered that the most important factor in synthetic resin emulsion adhesives used for high-speed adhesion, especially high-speed adhesion at linear speeds of 10 m/min or more, is its flow characteristics, and as a result of various experiments, found that high-speed adhesion The present invention was completed based on the discovery that it is necessary to have giratant flow characteristics.

(Object of the invention) Therefore, the object of the present invention is to provide a high-speed adhesive that satisfies both initial adhesion and mechanical properties.
In particular, the present invention relates to a high-speed adhesive used when mechanically bonding thin paper with a large air permeability at a linear speed of about 10 m/min or more.

(Structure of the Invention) The first feature of the present invention is that the high-speed adhesive is a synthetic resin emulsion having dilatant flow characteristics.

Before explaining the present invention, the flow characteristics of synthetic resin emulsions will first be briefly explained. In general, emulsicons are non-Newtonian, which means that the apparent viscosity decreases as the shear rate increases (pseudoplastic flow, and conversely, the apparent viscosity increases as the shear rate increases). Dilatant flow can be roughly divided into two types of flow characteristics:

Relatively high concentration, high viscosity emulsions, such as those used in adhesives, generally exhibit pseudoplastic flow. The phenomenon in which the viscosity shows a time-dependent isothermal reversible decrease is generally referred to as thixotropy, and this is a phenomenon corresponding to the above-mentioned plastic flow.

The viscosity behavior where the viscosity changes as a result of changes in shear rate is called structural viscosity, and to express the degree of this structural viscosity, the rate of change in viscosity with respect to changes in shear rate is used as the structural viscosity index.

When a B-type viscometer is used, the rotor is set at a constant temperature, the viscosity (η) and the rotor rotational speed (ω) are taken as logarithms, and the rate of change (b) is used as the structural viscosity index. That is, these relationships are eog yy = log a + b lJog ω
It is represented by -・------(I). For convenience, use a B-type viscometer rotor 3 and set the speed at 6 rpm and 5 Q rpm.
Ratio η(6/60) of each viscosity η(6) and η(60) at
If this value is less than 1, it can be said to be giratancy, if it is 1, it is Newtonian, and if it exceeds 1, it can be said to be titanium tropy.

In the present invention, the above-mentioned structural viscosity index (b) is positive, that is, it has dilatant flow characteristics, and other adhesive properties, such as the above-mentioned initial adhesion and mechanical properties, are equal to or higher than those of conventional adhesives. Emulsicone, a synthetic resin held in an adhesive, is used as a high-speed adhesive. In the past, several synthetic resin emulsions exhibiting dilatant flow properties have been reported in the course of research on emulsion physical properties. can get. However, it is clear that even if the adhesive has only giratant flow characteristics, it cannot be used as a high-speed adhesive unless the above-mentioned initial adhesion and mechanical properties are satisfied. The inventor of the present invention has found that it is possible to meet various demands for a high-speed adhesive by improving the flow characteristics of the adhesive to give it giratant flow characteristics while maintaining the adhesive strength of conventional adhesives. This is what was discovered.

Synthetic resin emulsions to which the present invention can be applied include any conventionally known emulsions, particularly vinyl acetate homopolymer-based aqueous emulsions, polyethylene vinyl acetate copolymer-based aqueous emulsions, and acetic acid-vinyl copolymer-based aqueous emulsions. Emulsions are preferred.

Although the high-speed adhesive of the present invention is mainly used for bonding paper, it is clear that it can be applied to other materials that require high-speed bonding.

Methods for imparting dilatant flow properties to conventional adhesives while retaining their adhesive strength can be broadly classified into two types: 1) By polymerization 2) By composition (during polymerization and/or compounding).

The high-speed adhesive with giratant flow properties according to the present invention can be applied to a wide range of synthetic resin emulsions by methods (1) and/or (2) above.

The present invention will be explained below using specific examples.

(2) Manufacturing method of dilatancy adhesive A1 By polymerization Hereinafter, the method for manufacturing the dilatancy adhesive of the present invention will be explained using examples. However, it is clear that the present invention is not limited thereto.

1 part Mg Example 1) - Vinyl acetate homopolymer emulsion B
Into a four-bottle flask with a capacity of 11 and equipped with a thermometer, a stirrer, a condenser, a dropping funnel, etc., was added 123.
5 parts (by weight, same below), 100 parts of vinyl acetate, polyvinyl alcohol (degree of saponification 95%, molecular weight 600-1
Add 8.5 parts of 700) and raise the temperature while stirring.
When the temperature reached ℃, 02 parts of hydrogen peroxide was added and further 80
Polymerization was carried out for 2 hours while maintaining the temperature at °C, and after 2 hours, 15 parts of dibutyl phthalate (DBP) was added dropwise over 1 hour. The emulsion was then aged at 85°C for 2 hours.

The viscosity of the obtained emulsion was measured using a B-type viscometer (rotor N
cL3). Rotation speed is 5 rpm5 Q
The apparent viscosity ratio η (6/60) at rpm is 0.
It was 9. The adhesion failure rate of this emulsion is 49.
It was 6. (Note: The adhesion failure rate is 1 when using a cigarette attachment machine with a production capacity of 4000 pieces/minute.
Example 2 - Vinyl acetate homopolymer emulsion - In the same apparatus as in Example 1, 125 parts of deionized water and polyvinyl alcohol (with a degree of saponification of 95 mo7% and 92%) were added.
Add 10 parts of 1% mai (mixed with 1=1), heat up, add potassium sulfate, and while maintaining the temperature at 80°C, add 33 parts of vinyl acetate dropwise over the first 60 minutes. Next, 67 parts of vinyl acetate and 15 parts of dibutyl phthalate were added dropwise over 2 hours to carry out polymerization. then 85
Aging was performed at ℃ for 2 hours.

η('6/60)Ho of the obtained emulsion, 9T
The adhesion failure rate was 5o.

(Comparative Example 1) The same operation as in Example 1 was performed, but dibutyl phthalate was not added during polymerization. In this case η(6/60)
was 1.3, and the adhesion failure rate was 600.

(Comparative Example 2) The same operation as Comparative Example 1 was performed, but dibutyl phthalate was added after the emulsion reached room temperature after polymerization, and dibutyl phthalate was added after the emulsion was further heated to 80°C. However, in both cases, η(6/60) was 1.2 and the adhesion failure rate was 700.

(Example 3) - Vinyl acetate copolymer emulsion - Using the same equipment as in Example 1, 108.5 parts of deionized water and polyvinyl alcohol (saponification degree 92 mo1%) 8.
After raising the temperature to 70°C, 0.2 parts of potassium persulfate was added, and after further heating to 80°C, 100 parts of a vinyl acetate/diptylphate (90:10) mixture was added over 2 hours. Then, it was further aged for 2 hours.

The obtained emulsion has η(6/60) of 0.89,
The adhesion failure rate was 90.

(Example 4, 5.6) Monoacetate/l/nia ;f! IJmer-based emulsion*7 Dioctyl maleate (I'DOM), butyl acrylate (BA
), and the same procedure as in Example 3 was performed except that acrylic acid (AA) was used. The results obtained are as follows.

Example Copolymerization monomer η (6/60) Adhesion failure rate (4 DOMO,
9705BA O, 9110 6AA O, 85140B, by Taka The high-speed adhesives according to the invention can also be easily produced by adding inorganic electrolytes to the emulsion H). In particular, when a polymer having a hydroxyl group such as polyvinyl alcohol is present, deol-type intramolecular and/or intermolecular crosslinking occurs between the inorganic electrolyte and the hydroxyl group, thereby developing dilatant properties. 0 The above inorganic electrolytes include poval gelling agents and known materials such as sulfates such as Na2SO4, (MH,)2So4, nitrates such as NH4NO3, phosphates such as Na3PO4, organic salts such as potassium citrate, Examples include boric acid and borax. The amount of these inorganic substances added varies depending on the type of emulsion. The emulsion itself may or may not be a guilency.

Examples of dilatancy adhesives with addition of inorganic electrolytes will be described below.

(Example 7) A high-speed adhesive having the following composition was prepared using vinyl acetate emulsion prepared by a conventional method.

Vinyl acetate emulsion 69.22 parts Dibutyl phthalate 4.97 parts Antifoaming agent ('N0PCO-8034') 0.
30 parts Preservative (Suraoff-72N) 0
．． 10 parts 5% H3BO35, 60 parts 100.00 The physical properties of this adhesive composition were as follows.

NV 48 viscosity (rotor N113.3Orpm) 1220CPSP
H4,6 PVA 15PHRDBP
30 PHR The flow properties of this composition were η(6/60)=0.95, and the adhesion failure rate was D=100.

■ Dilatancy adhesive and high-speed adhesive properties The relationship between the dilatancy adhesive and high-speed adhesive properties will be explained below.

The performance of adhesives that can be used with high-speed adhesive machines includes initial adhesion,
Roll 1: There are many factors such as belling property, storage stability, re-emulsifying property, etc., but in order to comprehensively evaluate these, we conducted an actual machine test using a high-speed bonding machine that is actually used, and evaluated the adhesion failure rate as a result. The most reliable method is to check the roll workability.

Today, cigarette tip attachment machines require high-speed adhesion at linear speeds of about 10 m/min or more, so the adhesive properties of the present invention were evaluated using this machine.

1) Measurement of adhesion failure rate When wrapping chip paper around 4000 cigarette filter chips in 1 minute and adhering porous paper using a cigarette chip attachment (MMC-4000X 10000m 1 machine), the number of defective products was calculated. Total number 1
Expressed in units of 0,000 pieces. (Unit: 2 rolls) 2) Measurement of roll workability The amount of adhesive that scatters when the adhesive winding roll and the adhesive coating roll are brought into contact with each other and rotated in opposite directions at 33 Q rpm' for 30 minutes. It was attached to aluminum foil placed close to both rolls, and the amount was weighed (unit = m9).

Based on the measurement results of 1) and 2) above, the adhesive performance index (unit: book×m9) of the adhesive of the present invention was determined using the following relationship.

Adhesive performance index (F)=adhesion failure rate×scattering amount FIG. 1 shows the above adhesive performance index relative to 1 (6/60). As is clear from this table, it can be seen that as the adhesion speed increases, adhesives with dilatant structure viscosity are more suitable. Furthermore, it is clear that the value of r)(6/60) can be appropriately selected depending on the adhesion speed.

[Brief explanation of the drawing]

Figure 1 shows 6rp using a B-type viscometer rotor N113.
Fig. 3 is a diagram showing the relationship between the ratio of viscosity (1 (6/60)) at m and 5 Q rpm and the adhesive performance coefficient (F = adhesion failure rate x amount of scattering) as the production speed of the tobacco chip attachment machine is changed.

Claims (1)

[Scope of Claims] 1) A high-speed adhesive characterized by being composed of a synthetic resin emulsion having dilatant flow characteristics. 2) The synthetic resin emulsion according to claim 1, wherein the synthetic resin emulsion contains at least one of a vinyl acetate homopolymer-based aqueous emulsion, an ethylene vinyl acetate copolymer-based aqueous emulsion, and a vinyl acetate copolymer-based aqueous emulsion. Fast adhesive. 3) The high-speed adhesive according to claim 1, which is used for a high-speed paper bonding machine.