JPS58160378A - Emulsion type pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:To provide the titled adhesive exhibiting well-balanced bonding and cohesive powers and an excellent anchoring property, prepared by using a specified carboxy-modified styrene/butadiene copolymer latex as base polymer. CONSTITUTION:The adhesive is prepared by adding carboxymodified styrene/ butadiene copolymer latex with a carboxymodification degree of 0.5% or higher, a butadiene content of 50% or higher and a gel content of 35-65% to an aqueous emulsion obtained by blending an aqueous solution of an emulsifier into a solution of a mixture of a softener (e.g. paraffin-base extending oil) and a tackifier.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an emulsion-based adhesive using carboxy-modified SBR latex as a pace polymer, which is used for adhesive paper and adhesive tape. Carboxy-modified styrene with a coefficient of 50 or more and a gel fraction of 35 to 65.
Butadiene copolymer latex is used as a pace polymer,
This relates to an emulsion-type pressure-sensitive adhesive that is made by blending an emulsion of a softener and a tackifier with this adhesive, and in particular, the gel fraction (amount of toluene-insoluble components) representing the amount of crosslinking components of the Latinx is reversed. It is based on the discovery of a fact that serves as a guideline for the amount of low molecular weight components and is one of the main factors determining adhesive properties. More specifically, as a result of intensive study on the influence of the gel fraction of carboxy-modified SBR latex on adhesive properties, we decided to define the gel fraction of the latex within the range of 35 to 65 and use it as the base polymer. The present invention has led to the invention of an emulsion-based adhesive that maintains a good balance between adhesive strength and holding or cohesive strength, and has excellent anchoring properties.

Conventionally, solvent rubber-based adhesives have been used in adhesive products, but emulsion-based adhesives have been developed in recent years from the viewpoint of resource conservation, pollution, disaster prevention, and environmental issues.For example, acrylic emulsion-based adhesives have high adhesion. It is used to take advantage of its characteristics such as strength and weather resistance. However, acrylic emulsion-based pressure-sensitive adhesives have the drawbacks of low 1ti force on polyolefin films and the like, and high cost.

The present invention uses an inexpensive carboxy-modified SBR latex as a base polymer, and uses a compounding technology based on the discovery that the gel fraction of the latex determines the adhesive properties. It provides a rubber emulsion-based adhesive that has well-balanced adhesive properties and good adhesion to polyolefin films, etc.For adhesives using 08BR latex as a base polymer, the tackifier JP-A-52-93454, JP-A-53-. No. 56233 mentions SBR latex or carboxy-modified SBR latex as an example of the base polymer used, but no claim is made specifying the same. Furthermore, in JP-A No. 55-48270, regarding the emulsion adhesive using carboxy-modified SBR latex, the degree of carboxy modification of the latex and the styrene/butadiene ratio (S/B
However, there is no claim regarding the gel fraction.

When designing the formulation of adhesives, the molecular weight distribution of the base polymer and the amount of low molecular weight components are important.For example, as is well known in the case of solvent rubber adhesives, low molecular weight components are generated during the mastication process of natural rubber. Adhesives are prepared using Mooney viscosity as a guideline. Furthermore, in the production of adhesives using natural rubber latex as a base polymer, so-called depolymerized natural rubber latex (for example, manufactured by Aoi Ban Co., Ltd.), which is obtained by depolymerizing the lax to produce a low molecular weight component, is used. The present inventors have determined that by using the gel fraction, which indicates the amount of crosslinked components measured as toluene-insoluble components of SBR latex, as a guideline for the amount of low molecular weight components, the gel fraction can be determined based on the formulation design and quality control of the adhesive. The present invention was developed by paying attention to the fact that it is extremely useful.

As is well known, the gel fraction is expressed by the following formula, which is expressed as a component insoluble in a solvent such as toluene, which is obtained by converting latex to alkali to form a coagulated body.

Gel fraction (chi) = (1--)X100A: SBR
Total amount of sample of latex coagulate (g) Amount of toluene soluble component of BAA (g) The Kel fraction is useful as a guideline for the amount of low molecular weight component contained in the non-crosslinked component which is important for the development of adhesive properties.

In JP-A No. 55-48270, the degree of carboxy modification and S/
The content states that a commercially available SBR latex that satisfies the claimed range of B ratio can achieve the target adhesive properties, and there are no regulations regarding the molecular weight distribution or the amount of low molecular weight components. However, in the present invention, the gel fraction that we adopt as a guideline for low molecular weight components usually ranges over a wide range from 90% to 0% in commercially available latex. Unless the amount of low-molecular-weight components is controlled by specifying the ratio, it is impossible to actually design the composition of the adhesive properties and control the quality of the adhesive performance.

The present inventors have worked diligently to develop a rubber emulsion-based adhesive that is inexpensive and has average adhesive properties suitable for general-purpose applications, using SBR latex as a base polymer.
We discovered that the gel fraction, which indicates the amount of crosslinked components in the polymer of R latex, is not just a guide for low molecular weight components, but is an important factor that determines the adhesive properties. From the viewpoint of quality control, by intentionally setting the gel fraction of SBR latex to around 50%, a balance between adhesive strength and holding power or cohesive strength can be achieved, and the anchoring power of the adhesive product to the surface substrate can be achieved. The present inventors have discovered that it is possible to obtain a pressure-sensitive adhesive that has excellent properties and has good adhesion to polyolefin films, etc., and has thus come to form the present invention.

The characteristics of the present invention will be clarified by explaining in detail the formulation technology for creating an adhesive using SBR latex as a base polymer and the relationship between SBR latex and adhesive physical properties.

When selecting the SBR latex, which is the base polymer of the rubber emulsion adhesive of the present invention, three factors are considered as factors that determine the adhesive properties: the presence and extent of carboquine modification of the SBR latex, the SZB ratio, and the gel fraction. It became clear what had to be done.

That is, (a) to obtain an adhesive that has high adhesive strength (180° peel adhesion strength, loop tack), storage stability, anchoring ability to the surface substrate, and mechanical stability necessary for coating, a carboxy-modified type is used. is preferable, and the degree of carboxylation is 0.5 to 7.
．． 0 person is preferable.

(b) In order to obtain rubber elasticity and provide low-temperature physical properties to the adhesive, it is butadiene-rich and the glass transition point (Tg) is better.
HaS//13=40/6o~25/7. is optimal.

As the amount of butadiene increases, the adhesive strength increases, and as a reflection of the decrease in Tg, the low-temperature properties of the adhesive performance improve, and the lower limit temperature at which sticking is possible decreases. However, on the other hand, if the cohesive force decreases and the amount of butadiene becomes excessive, it is difficult to obtain a practical cohesive force or retention force. The amount of gel components insoluble in the solvent (toluene) due to crosslinking components in the resin (C%) is used as a guideline for the content of non-crosslinked components and low molecular weight components. That is, the lower the gel fraction, the more low molecular weight components there are. Carboxylation degree (5,
A carboxy-modified SBR latex (manufactured by JSR) prepared by hot polymerization with a constant S//I3 ratio (4°/6o) and a gel fraction in the range of 90 to 30 parts was obtained. When the tensile strength properties of the latex alone film were measured, the yield strength and breaking strength decreased as the gel fraction decreased, while the breaking elongation increased (Example 1-1). An adhesive prepared by the method described below using the latex as a base polymer exhibited the following adhesive properties depending on the gel fraction of the SBR latex (Example 1-2).

That is, the adhesive strength (180° adhesive strength, loop tack) of the pressure-sensitive adhesive tends to increase and become saturated as the gel fraction of the SBR latex decreases (low molecular weight components increase). In addition, the surface base material of adhesive paper (high-quality paper, coated paper, etc.),
Alternatively, the anchoring ability of the adhesive tape to the tape base material (kraft tape base paper, etc.) is improved.

The compatibility between SBR latex and compounds such as tackifiers and softeners is extremely important for the development of adhesive performance, and the degree of haze of the adhesive serves as a guideline for this.

It can be seen that as the gel fraction Cif of SBR latex decreases, the degree of haze decreases and the degree of compatibility increases.

From the above, the lower the gel fraction of SBR latex, the higher the amount of low molecular weight components.
It is thought that the compatibility with the R polymer increases, and the mobility and diffusion rate of the adhesive molecules also increase, resulting in improved adhesive strength, initial adhesive strength, and anchoring ability. On the other hand, the cohesive force of the adhesive decreases as the gel fraction decreases, and this phenomenon corresponds to the decrease in yield value and breaking strength obtained in the tensile strength test of SBR single films. The dependence of the adhesive force, cohesive force, and holding force of the pressure-sensitive adhesive on the gel fraction of SBR latex is schematically shown in the figure based on Example 1-2.

Adhesive force and cohesive force show contradictory increasing and decreasing trends with respect to gel fraction. Retention force is a physical property that appears as a synergistic effect depending on adhesive force, cohesive force, and the diffusion rate of adhesive molecules.
The maximum value of the holding force was expressed in the region where the gel fraction of SBR latex was around 50q6, and the adhesive that provided the maximum value of the holding force showed results corresponding to good corrugated board sealability. Therefore, in order to obtain an adhesive with a good balance between adhesion and holding or cohesive force and excellent anchoring properties, the gel fraction of SBR latex should be 35 to 65%, preferably 50±5%.
It is best to use carboxy-modified SBR latex. This will be explained in detail using Examples 1-2 and 1'-2.

The rubber emulsion pressure-sensitive adhesive using the SBR latex of the present invention as a base polymer is an emulsion of a mixture of a tackifier, a softener, and auxiliary materials such as anti-aging agents, and a gel component as claimed in the present invention. and S/B ratio of carboxy-modified SBR latex. For formulations containing tackifiers and softeners as main components, the aqueous solution of the emulsifier is added to the dissolved mixture obtained by dissolving them in advance using a solvent or by heating and melting them to generate a sufficient shear force for emulsification. Create an emulsion under stirring and mix the emulsion with SBR.
A rubber emulsion type adhesive is prepared by mixing with latex and increasing the viscosity if necessary.

Tackifiers include gum rosin, wood rosin, or tall oil rosin, derivatives such as garlic, phenolic resins,
Terpene resin, chroman/indene resin, or petroleum resin (aliphatic, aromatic, and copolymers thereof)
In some cases, two or more types of tackifiers or resins with different softening points are used in combination. Furthermore, it is also possible to use an emulsion of a commercially available tackifier.

As the softener, a paraffinic, naphthenic, or aromatic extender oil is used, and if necessary, a plasticizer or a liquid tackifier is used in combination.

・Hereinafter, we will clarify the influence of the gel fraction of carboxy-modified SBR latex on the adhesive properties of adhesives based on this latex, and we will demonstrate the effect of the adhesive strength by using carboxy-modified SBR latex with a gel fraction of 35 to 65%. It will be described based on examples that it is possible to obtain a rubber emulsion-based pressure-sensitive adhesive that has adhesive performance that is well-balanced with holding power or cohesive force, and has good anchoring properties.

Example 1 Carboxy-modified 11BR latex by pot polymerization with different gel fractions (90-30%) (degree of carboxy-modification -5,0% *''/B) iS-40/60,
JSRiA) was used to measure the tensile strength properties of an SBR single film (Example 1-1), an adhesive was prepared using the latex 1, and the influence of gel fraction on adhesive properties was determined (Example 1-1). Example 1-2), gel fraction is 50±
It was found that 5% gave the most well-balanced adhesive performance.

Example 1-1 Single films of seven types of carboxy-modified SBR latex with different gel fractions (90 to 30%) were prepared and tensile strength tests were conducted, and yield stress, breaking stress, The dependence of elongation at break on gel fraction was determined.

The measurement results are shown in Table 1.

As is clear from Table 1, as the gel fraction of SBR latex decreases, the yield strength and breaking strength of the latex single film decrease, and the elongation at break increases, reflecting the increase in low molecular weight components. Incidentally, the haze degree of the SBR single film does not depend on the gel fraction and is at almost the same level.

0) Gel rate: SBR latex with NaOH (30%
) was added dropwise to coagulate at pH 2.7, and then dried under vacuum. The toluene-soluble components of the dried coagulate (g) were extracted, and the extracted amount component 0'3) was determined from the following formula. .

Gel fraction = (14) x 100chi.

Q) Use haze meter ND-H67 (Nippon Heavy Industries) (3
) Latex was cast on a Teflon plate with a frame, dried in a gear oven (90°C x 6 hours), and a strip for tensile strength test: 10 mm (width) x 1. Omm (thickness) x
loomm (length) was created.

Tensile strength test conditions Tensile speed: 100 mm/In1n Distance between chucks: 10 mm One mark of yield strength is the maximum yield value of the stress-cured elongation curve.
No marks were obtained as extrapolated values before and after yielding.

Example 1-2 Carboxy-modified SBR with different gel fractions of Example 1-1
Using latex (A-G), an adhesive was prepared according to the formulation shown in Table 2 in the following manner. The mixture of tackifier, softener, and anti-aging agent shown in Table 2 was heated (95°C) and dissolved, and after complete dissolution, the melt temperature was lowered to about 70°C, and an emulsifier (trade name: DRA-4000) was added. An aqueous solution of polyoxylodine ester HLB=17) was added, and an emulsion was obtained under stirring. Further, according to the formulation in Table 2, SBR and latex were added and mixed, and a thickener (Latechol D; sodium polyacrylate) was added and thoroughly stirred to obtain a solid content of 6.
Seven types of adhesives with a coefficient of zero and a viscosity of approximately 15,000 cps (25°C) were prepared. Transfer the prepared adhesive to the kraft tape base paper under drying conditions of -110°C.
A kraft tape was prepared by coating 45 i9/m2 in 6 minutes, and the adhesive properties of the tape were measured. The haze degree of the adhesive is determined by coating the adhesive on a PET film (50 ul) (4
The cloudiness was measured using a 5-axis 2) cloud meter. The results are shown in Table 6.

Margin table 2 below: Formula 1 Haze degree: Coat the adhesive on PET film (25μ) and measure with haze meter (Nippon Heavy Industries ND-H67) 2 Anchoring ability: Match the adhesive sides of the coated ensemble together and subtract. Anchoring ability to the surface base material (kraft tape base paper) when peeled off ×; Poor △; Slightly good ○; Good 6 Adhesive strength z180° peeling, tensile speed against stainless steel:
300 mm/min.

20℃, AF interfacial failure, CF cohesive failure 4 Loop tack z vs. cardboard, tensile speed; 5o・o””/m i
n, 20℃5 Ball tack: J, I)o
W method θ-60°, 20℃6 Holding crab vs. cardboard, pasting area 1.25X1・25t:rn.

Load: 5009r AF interfacial failure, CF cohesive failure 7 cohesive crab adhesive surfaces, pasting area 1.25x1°25cm.

Load: soogr 8 Cardboard seal 1 cow: Cardboard box pasted area 5
, Ocm x 2.5 cm, and the sealing property is indicated by the seal retention rate (number of areas where the adhesive does not peel/total number of adhesive areas). (mrr+) (20℃, 65 coefficient R) It's expensive enough to be a dog.

That is, the compatibility is low. On the other hand, as the gel fraction decreases, the degree of haze of the adhesive decreases and the compatibility increases.

When the adhesive was applied to kraft tape base paper by the transfer method, the anchoring ability of the adhesive to the base paper clearly became better as the Kel fraction of the SBR latex decreased.

Adhesion strength and initial adhesive strength (loop tack value) are also SBR
As the gel fraction of latex decreased, it tended to increase and become saturated.

On the other hand, the ball tack value showed no dependence on the Kel fraction and showed a roughly constant value.

The cohesive force decreased as the Kel fraction of SBR latex decreased.

As mentioned above, the dependence of the haze degree, anchoring ability, adhesive force, initial adhesive force, and cohesive force on the gel fraction of SBR latex, which is the base polymer, is determined by the tensile strength physical properties of SBR single film (Example 1-11 Table 1 ) corresponds well to the gel fraction dependence of SBR latex, which clearly reflects the decrease in the gel fraction of SBR latex, that is, the increase in low molecular weight components.

On the other hand, the holding force against cardboard increased as the gel fraction decreased, and reached an extremely large value near the gel fraction of 50 inches. This phenomenon is considered to occur because the holding force is a synergistic effect of adhesive force and cohesive force.

The gel fraction dependence of adhesive force, cohesive force, and holding force is schematically illustrated based on the results in Table 6. Adhesive V using SBR latex with a gel fraction of -50%, in which the synergistic effect of adhesive force and cohesive force, which show contradictory tendencies with respect to the gel fraction, is most highly expressed showed the maximum holding power. Adhesive V also showed the best results for corrugated board sealability, which is a practical performance requirement for craft tapes. The corrugated cardboard sealability corresponds to the ability of the cardboard box to not flap after sealing, which corresponds to the good holding power of the adhesive V to the corrugated cardboard.

Adhesive V using SBR and Latex E with a gel fraction of 50q6 has a good balance between adhesive strength, initial adhesive strength (loop tack), and retention or cohesive strength.

It has excellent corrugated sealing properties and exhibits adhesive performance comparable to acrylic emulsion-based adhesives and bath agent-type natural rubber-based adhesives.

Example 2 Using the adhesive V (Table 6) prepared in Example 1-2, adhesive paper was coated with 25"72 (solid content) by a transfer method on high-quality paper (basis: 50 g/m"). It was prepared and its adhesive properties were measured. Table 4 shows a comparison of the adhesive physical properties with that of an acrylic emulsion adhesive.

5f3R latex adhesive ■ exhibits almost the same adhesiveness as commercially available acrylic emulsion adhesives used for average general-purpose applications, and has excellent adhesion to polyethylene film and polypropylene film in particular, making it suitable for general adhesive paper. It had sufficient adhesive performance.

Table 4 Adhesive Example 3 of 5f3R engineered Mulchon adhesive (Adhesive V in Table 6) Kel fraction is approximately 5 based on the results of Example 1-1.1-2
Non-carboxy-modified SDR at 0%, latex (A-) and carboxy-modified type have different SA3 ratios (5015
0 to 50/70) latex (B, C, D), adhesives were prepared according to the formulation shown in Table 2, with only the amount of softener added being changed to 60 parts. The adhesive was applied to a craft tape base paper by a transfer method (4511//m2) to prepare a tape.

The adhesive physical properties are shown in Table 5.

Adhesive I using non-carboxy-modified SBR and latex A has poor anchoring properties to kraft tape base paper and low initial adhesive strength (loop tack). Furthermore, when the adhesive was roll coated with a Dixon coater, gum up occurred on the roll surface, resulting in poor mechanical stability during coating.

Carboxy modified type with S/B ratio of 5015.
0.40/60.30/7Q (7) SBR Latex, <
(B, C, DJ ita adhesive I [, III,
IVld(Mremoli) showed good anchoring properties and coating suitability. Ball tack, initial adhesive strength (loop tack)
Both increase as the amount of butadiene increases, and the low-temperature performance also becomes better, and the glass transition point (Ty, °C,
).

On the other hand, the holding force against cardboard decreased as the amount of butadiene increased.

From the above results, carboxy-modified SBR is superior in terms of initial adhesion and anchoring properties, and if the degree of carboxy-modification is excessive, problems such as hardening of the adhesive due to heat aging will occur, so it is generally A carboxy denaturation degree of 5 to 7.0 is desirable.

In addition, styrene-rich caratex with an S/B ratio of 50,750.11 has low pole tack, low initial adhesion, and
This is not preferable because low-temperature performance deteriorates as I increases. On the other hand, a butadiene-rich latex with an S/B ratio of 25/75 or less results in a decrease in holding power or cohesive force, making it less practical. Therefore, the SBR latex for rubber emulsion adhesive of this patent has a degree of carboxy modification of 0.5 to 7.
．． It is desirable that the S/B ratio be 40/60 to 25/75 at 0%.

[Brief explanation of drawings]

The figure shows the adhesive strength of the adhesive based on Example 1-2. Patent Applicant Sanyo Kokusaku Pulp Co., Ltd. Agent Patent Attorney Tadao Noma Patent Attorney Tadayuki Noma Keir Bunsha (0) Procedural Amendment April 15, 1980 Haruki Shimada, Commissioner of the Japan Patent Office 1, Special Request for Indication of Case 1982 - 42901 No. 2, Name of the invention Emulsion M Pressure Sensitive Viscous M Agent 6, Relationship with the person making the amendment Patent applicant address 1-4-5 Marunouchi, Chiyoda-ku, Tokyo Name (
234) Sanyo Kokusaku Pulp Co., Ltd. President Ninomiya
Masayoshi 4, Agent 100 Address 1-4-5 Hiraku Building 2, Marunouchi, Chiyoda-ku, Tokyo
Room 64 Telephone: 214-2861 Name (64)
83) Patent Attorney Tadao Noma Address Same Name (71110) Patent Attorney Tadayuki Noma 5, Voluntary Correction 6, Claims column and Detailed Description of the Invention column of the specification to be amended Z Contents of the amendment In the specification We will correct the following points. (1) The scope of claims from page 1, line 4 to page 2, line 10 will be amended as shown in the attached sheet. (2) Page 5, line 8, ``For example, made by Aoi Uban'' has been corrected to ``For example, made by Aoi Ubar''. (3) On page 6, line 20, the phrase "gel fraction is simply" will be corrected to "gel fraction." (4) On page 7, line 7, "ole film" will be corrected to "olefin film." (5) Page 11, line 6 [Preferably! "bo't 5% J" means "preferably 5% J".
We will correct it as 0±5%. (6) In the first line of page 15, "(1) Gel fraction:" will be corrected to "(1) Gel fraction:". (7) Page 15, 2nd line [pH 2,7J] will be corrected to ``approx. 1) H = 7.DJ.'' (8) Table 2 on page 17 will be corrected as follows. 2. Combination prescription (9), page 26, left column 2 of Table 5, Claim 1 The degree of carboxy modification is 0.5% or more, the amount of I-bonded butadiene is 50% or more, and the gel fraction is 65 to 65%. An emulsion-type pressure-sensitive adhesive comprising a certain carboxy-modified styrene-butadiene copolymer latex as a base polymer and an aqueous emulsion of a softener and a tackifier added thereto.2 The carboxy-modified degree of the carboxy-modified SBR latex is 0.5 to 7 for styrene-butadiene copolymer
．． 2. The emulsion-based pressure sensitive adhesive according to item 1, wherein the pressure-sensitive adhesive is 0%. 6. The emulsion pressure-sensitive adhesive according to item 1, wherein the carboxy-modified SBR latex has a styrene/butadiene ratio of 20/80 to 50,150. 4 Is the softener paraffin-based? The emulsion pressure-sensitive adhesive according to claims 1 to 6, which is a tensile or aromatic extender oil. 5 The tackifier is gum rosin, wood rosin, tall oil rosin, or derivatives thereof, phenolic resin,
The emulsion-based pressure-sensitive adhesive according to claims 11 to 4, which is 1s or more of terpene resin, coumaron-indene If fat, and petroleum-based resin. 6 Claims 1 to M in which the emulsion contains an anti-aging agent and a thickening agent as auxiliary materials in addition to a softener and a tackifier.
The emulsion-based pressure-sensitive adhesive according to item 5. -51!

Claims (1)

[Scope of Claims] 1. A carboxy-modified styrene-butadiene copolymer latic having a carboxy modification degree of 0.5% or more, a bound butadiene amount of 50 parts or more, and a gel fraction of 35 to 65 parts as a paste polymer. An emulsion-type pressure-sensitive adhesive consisting of a water-based emulsion of a softener and a tackifier. 2 The degree of carboxy modification of the carboxy modified SDR latex is 0.5 to 7 with respect to styrene/butadiene copolymer.
．． The emulsion-type pressure-sensitive adhesive according to item 1, which has a coefficient of 0. 3. The emulsion type pressure sensitive adhesive according to item 1, wherein the carboxy-modified SBR latex has a styrene/butadiene ratio of 20/'80 to 50150. 4. The emulsion-type pressure-sensitive adhesive according to claims 1 to 3, wherein the softener is a paraffinic, naphthenic, or aromatic extender oil. 5 The tackifier is gum rosin, wood rosin, tall oil rosin, or derivatives thereof, phenolic resin,
The emulsion-type pressure-sensitive adhesive according to claim 1), which is one or more of terpene resin, coumaron-indene resin, and petroleum resin. 6. The emulsion-type pressure-sensitive adhesive according to claims 1 to 5, wherein the emulsion contains an anti-aging agent as an auxiliary material in addition to a softener and a tackifier.