JPH0819389B2 - Acrylic pressure sensitive adhesive composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition using an aromatic petroleum resin having a special chemical structure as a tackifier. More specifically, it is a polymer having a structure in which an aromatic ring is bonded via a methylene group, and an aromatic petroleum resin having no double bond or oxygen atom or containing no oxygen atom in practice is used as a tackifier. The present invention relates to a pressure-sensitive adhesive composition.

(Prior Art) As a main material of a pressure-sensitive adhesive, a natural or synthetic rubber type and acrylic type are mainly used. Acrylic pressure-sensitive adhesives are generally superior in heat resistance and weather resistance compared to rubber-based pressure-sensitive adhesives, and due to the large number of acrylic monomers used as raw materials, polymerization methods, compounding technology, and crosslinking technology are used. This has the advantage that various product requirements can be met.

Acrylic base polymers are generally synthesized by copolymerizing some acrylic monomers on the basis of certain acrylic acid esters. Acrylic ester mainly imparts tackiness, and other acrylic monomers have a role of imparting cohesiveness, adhesiveness, and crosslinking reactivity. Unlike rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives require almost no additional components such as tackifiers, plasticizers, etc., and are composed of only a copolymer component or a system obtained by reacting this with a crosslinking agent. Can be an adhesive. That is, the acrylic pressure-sensitive adhesive can be adjusted to have viscoelasticity suitable for the pressure-sensitive adhesive only with the acrylic base polymer.

(Problems to be Solved by the Invention) As described above, the acrylic pressure-sensitive adhesive is an adhesive having excellent properties, but in view of demands such as diversification of adherends and improvement of productivity, further adhesion Improved properties, especially adhesion to non-polar adherends such as polyethylene and polypropylene, are desired. Then, for the purpose of improving the adhesive force to the non-polar adherend, a method of adding a tackifier that is well compatible with the acrylic base polymer and can suppress the decrease of the adhesive force (tack) to a minimum is used.

Among tackifiers, naturally-occurring rosin-based resins such as rosin, rosin ester, and hydrogenated rosin ester resins improve adhesion to nonpolar adherends, and are highly polar acrylic base polymers. It is preferably used because it is well compatible with.

However, since rosin-based resins are naturally produced, their supply is unstable and expensive. Further, conventional aromatic petroleum resins can be used for this purpose because they are compatible with the acrylic base polymer, but they have the drawback of poor heat resistance and weather resistance.

As described above, since the tackifier has advantages and disadvantages,
Satisfactory acrylic pressure-sensitive adhesives using these are not available yet.

(Means for Solving the Problems) The present inventors have improved the adhesive force to non-polar adherends, and have not deteriorated the weather resistance, which is an advantage of acrylic pressure-sensitive adhesives, and have high polarity acrylic adhesives. In order to be compatible with the base polymer, firstly it has a wide compatibility range, secondly it has a chemical structure with a high affinity for non-polar adherends, and thirdly it has heat resistance and weather resistance. 3 of being good
We focused on the need for a tackifier with conditions.
Therefore, we examined the adhesive properties by mixing an aromatic petroleum resin having a chemical structure different from that of conventional aromatic petroleum resins with various acrylic base polymers. The acrylic pressure-sensitive adhesive composition containing and has adhesive properties such that the adhesive force and the holding power are improved without lowering the adhesive force (tack), and can be substituted with the same type composition using a natural resin. It has been found that it exhibits excellent adhesive performance.

That is, the present invention is an acrylic pressure-sensitive adhesive composition that uses an aromatic petroleum resin having a special structure as a tackifier and an acrylic resin as a base polymer.

The special chemical structure referred to here is an oligomer having a structure in which an aromatic ring is bonded via a methylene group, and has no double bond and oxygen atom other than the aromatic ring, or a structure that does not contain practically at all. It is considered that, due to this special structure, it has excellent heat resistance and weather resistance, and has a wide compatibility range.

(Function) The aromatic petroleum resin used in the present invention can be produced by reacting an aromatic compound or a fraction containing an aromatic compound as a main component with formaldehyde in the presence of an acid catalyst. First, toluene as the aromatic raw material,
Benzene derivatives such as xylene, ethylbenzene, methylethylbenzene, trimethylbenzene, dullene, isodurene, and the like, and benzene derivatives and indane derivatives in which 1 to 4 substituents having a relatively small number of carbon atoms such as methyl groups or ethyl groups are substituted, naphthalene, anthracene There is no particular limitation as long as it is a derivative of various condensed polycyclic aromatic compounds such as and the like, or a mixture thereof or a fraction containing a part thereof.
Even if an aromatic compound having a substituent having a relatively large number of carbon atoms such as a propyl group or a butyl group or a non-aromatic compound such as paraffin or naphthene is contained, these compounds are not reactive with formaldehyde. Since it is low or does not exist at all, it simply acts as a solvent, and the apparent resin yield is reduced, but there is no particular problem as long as the above-mentioned reactive aromatic compound is contained in the feed oil. . However, it is necessary to consider the content of the reactive aromatic compound in the feedstock when determining the molar ratio of formaldehyde to the feedstock described below. Thus, generally, toluene, a reforming-type or cracking-type mixed xylene fraction, a C ₉ or C ₁₀ aromatic fraction obtained from a bottom oil of xylene production or isomerization, etc. are practically preferable feedstocks. . Particularly, a C ₉ aromatic fraction is preferable.

Formaldehyde, which is one of the raw materials, may be in any form as a starting raw material as long as it produces monomeric formaldehyde in the reaction system, for example, commercially available various concentrations of formalin or trioxane and paraformaldehyde. Although such a polymer or the like can be used as it is, paraformaldehyde, which does not lower the catalyst concentration (formalin reduces the catalyst concentration because it is an aqueous solution) and is easily available at a low price, is most suitable.

Further, gaseous formaldehyde separately generated by some method may be dissolved in a raw material oil, a catalyst (if liquid), a solvent, etc. and charged into the reaction system.

The catalyst is not particularly limited as long as it is an acid catalyst, and sulfuric acid, phosphoric acid, pyrophosphoric acid, perchloric acid, aluminum chloride, boron trifluoride or the like can be used. Sulfuric acid is advantageous because it is cheap and easy to reuse. The solvent is not particularly necessary because an excess amount of the raw material oil acts as a solvent, but an appropriate amount of a solvent that does not participate in the reaction (eg, isoparaffin) can be added if necessary.

In order to obtain an aromatic petroleum resin containing neither oxygen atom nor double bond, the molar ratio of formaldehyde to the reactive aromatic compound needs to be suppressed to 1 or less, preferably 0.8 or less. Generally, the lower the molar ratio, the lower the yield of the produced petroleum resin and the lower the softening point, although it depends on the kind of the aromatic compound used as the raw material. The content can be decreased, and the higher the molar ratio, the higher the yield and the softening point, but the higher the content of oxygen atoms. Although it is possible to produce a petroleum resin even when the molar ratio is greater than 1, the content of oxygen atoms is high and the catalyst separation operation becomes difficult under the practical reaction conditions described below.

The amount of the catalyst used in this reaction cannot be specified unconditionally because it is closely related to the reaction conditions, but it is generally 5 to 50% by weight, preferably 15% by weight with respect to the reactive aromatic compound in the feed oil.
~ 35 wt% is suitable.

The reaction temperature of this reaction depends on the type and amount of the feed oil and the catalyst and cannot be specified unconditionally, but is generally 60 to 180 ° C, preferably 80 to 120 ° C.

The reaction time related to this reaction cannot be specified unconditionally because it depends on the type and amount of the feed oil and the catalyst, and the oxygen content of the petroleum resin produced decreases with the reaction time. Can be regarded as not containing at all,
The time to decrease to 1.0% by weight or less, generally 0.5 to 10 hours, preferably 2 to 5 hours is used.

The desired aromatic petroleum resin is obtained by removing the catalyst from the reaction product, washing (removing a trace amount of acidic substance), unreacted oil, solvent (when used) and light product.

The final distillation condition cannot be unconditionally specified because it depends on the type of feedstock oil and the desired properties of the target aromatic petroleum resin, but it is usually under a reduced pressure of 5 mmHg or less, preferably 2 mmHg.
The desired aromatic petroleum resin is obtained by distilling off the light components at 300 to 470 ° C. at atmospheric pressure under the following reduced pressure.

The aromatic petroleum resin thus obtained is mainly composed of an oligomer having an aromatic ring and a methylene group alternately bonded to each other and having an aromatic ring or a methyl group at a terminal, and has no double bond or oxygen atom. It is a resin that does not exist or is not contained at all in practical use. Here, having no double bond, or not containing at all practically means having a bromine number of 1.0 or less, and having no oxygen atom or not containing at all practically 1.0% by weight of oxygen. It means the following.

The acrylic base polymer used in the present invention is not particularly limited as long as it is an acrylic base polymer compatible with the aromatic petroleum resin.

Further, since the aromatic petroleum resin does not significantly inhibit the polymerization reaction and crosslinking reaction of the acrylic monomer, it can be added before the polymerization or before the crosslinking.

The compounding ratio of the composition according to the present invention is 1 to 100 parts by weight of the aromatic petroleum resin, preferably 2 to 40 parts by weight, relative to 100 parts by weight of the acrylic base polymer, and addition of a filler and the like as necessary. The agent can be added in any mixing ratio.

(Examples) Examples will be shown below for clarifying the content of the present invention, but the present invention is not limited thereto unless it exceeds the gist.

In the practice, the softening point and bromine number of the produced aromatic petroleum resin were measured according to JISK-2207 and JISK-2605, respectively, and the oxygen content was measured by an elemental analyzer. It was confirmed by an elemental analysis, infrared spectroscopic analysis, nuclear magnetic resonance analysis, vapor pressure equilibrium method (VPO) analysis, and structural analysis by gel permeation chromatography that the aromatic ring was an oligomer bonded through a methylene group. .

Heat resistance was measured by taking 50 g of resin in a glass container (30 mmφ × 100 mm), aging it at 150 ° C. in a gear oven, and measuring changes in hue and viscosity with time.

The weather resistance is 80-90 μm on a glass plate, and the temperature is 63 ° C and the humidity is 60 in a sunshine weatherometer.
%, For 120 minutes in 120 minutes, the change in appearance was observed after exposure under rain conditions. Next, a method for producing an aromatic petroleum resin used in the present invention is shown in Reference Examples 1 and 2, and a method for producing an acrylic base polymer used for comparison is shown in Reference Example 5.

Reference Example 1 240 g of a C ₉ aromatic fraction having a boiling range of 150 to 180 ° C. of a reforming bottom oil of xylene in a four-necked flask equipped with a stirrer and a reflux condenser and 20 g of commercial industrial 92% paraformaldehyde.
Was added, and commercially available 75% dilute sulfuric acid 75% was added dropwise with slow stirring. After adding sulfuric acid, adjust the reaction temperature to 10 using an oil bath.
The temperature was raised to 0 to 110 ° C., and the reaction was continued for 3 hours with vigorous stirring. After completion of the reaction, the mixture was cooled to room temperature, and the contents were transferred to a dropping funnel and left to stand, so that a sulfuric acid layer was separated into a lower layer, which was removed.

Subsequently, washing with water was repeated 2-3 times until the pH of the washing water showed 7. Transfer the resulting oil layer to a distillation flask, initially about 10
Finally, the degree of vacuum was raised to 1 mmHg by vacuum distillation at mmHg to remove light components below 360 ° C. at atmospheric pressure, and 134 g of the target aromatic petroleum resin was obtained in the bottom of the kettle. The obtained petroleum resin has a softening point of 88.5 ° C, a bromine number of 0.2gBr ₂ / 100g, and an oxygen content of
It was 0.1% by weight or less, and it was clarified that neither oxygen atom nor double bond was contained practically. The resin obtained by this reaction is referred to as aromatic petroleum resin 1.

Regarding the heat resistance and weather resistance of the obtained petroleum resin,
Shown in Tables and Table 2.

Reference Example 2 After using the same equipment as in Reference Example 1 under the same feed oil and under the same conditions to carry out reaction, catalyst removal and washing with water, finally 1 mmHg
Under reduced pressure to distill away light components below 460 ° C at atmospheric pressure,
112 g of the target aromatic petroleum resin was obtained. The resulting softening point of the petroleum resin is 117.5 ° C., Bromine Number 0.3g Br ₂ / 100g, oxygen Motoritsu was 0.1% by weight or less. The resin obtained by this reaction is referred to as an aromatic petroleum resin 2.

Regarding the heat resistance and weather resistance of the obtained petroleum resin,
Shown in Tables and Table 2.

Reference Example 3 As a conventional aromatic petroleum resin, a commercially available C ₉ petroleum resin (120 grade) was selected.

Softening point 122.0 ° C., Bromine Number 28.0g Br ₂ / 100g, oxygen Motoritsu was 2.0 wt%.

The heat resistance and weather resistance of this resin are shown in Tables 1 and 2
Shown in the table.

Reference Example 4 A commercially available hydrogenated rosin ester (softening point 74 ° C.) was selected as a conventional natural resin.

The heat resistance and weather resistance of this resin are shown in Tables 1 and 2
Shown in the table.

Reference Example 5 Acrylic base polymer is 70 parts by weight of 2-ethylhexyl acrylate as a soft monomer, 30 parts by weight of vinyl acetate or butyl methacrylate as a hard monomer,
Using 1 part by weight of acrylic acid, 120 parts by weight of ethyl acetate, and 20 parts by weight of isopropanol, azobisisobutyronitrile was used as an initiator and polymerized by a conventional method. Acrylic base polymer 1 (glass transition point -39 ° C) using vinyl acetate as the hard monomer and acrylic base polymer 2 (glass transition point -40 ° C) using butyl methacrylate were used.

Examples 1 to 8 and Comparative Examples 1 to 6 For the purpose of evaluating the performance of the acrylic pressure-sensitive adhesive composition, the properties of the acrylic base polymer 1 or 2 synthesized in Reference Example 5 and the properties of the acrylic base polymer 1 or 2 were used in Reference Example 1 or 2. Synthesized aromatic petroleum resin 1 or 2 and Reference Example 4 for comparison
Of commercially available hydrogenated rosin ester is mixed in a predetermined stoichiometric ratio to produce a pressure-sensitive adhesive. After removing the solvent on a polyester film having a thickness of 100 μm, the pressure-sensitive adhesive is applied with a coater to a thickness of 40 μm and the temperature is 100 ° C. And dried for 10 minutes.

The evaluation test uses the following methods for tackiness, tackiness,
The three adhesive properties of holding power were evaluated.

(1) Ball tack J. Under the conditions of running distance 10 cm, inclination angle 30 degrees, and temperature 22-23 ℃.
It was measured using the Dow rolling ball tack method, and the results were expressed as the maximum diameter of a stationary ball (X1 / 32 inch).

(2) Adhesive strength Adhesive tape with a width of 25 mm is attached to a steel plate or polyethylene plate adherend and peeled in the direction of 90 degrees at a speed of 300 mm / min.
The load required for the peeling was measured.

(3) Holding power Adhesive tape is applied to the steel plate adherend with an area of 25 mm × 25 mm,
The time until falling when a load of 1 kg was applied was measured.

 The results are shown in Table 3.

(Effect of the invention) The acrylic pressure-sensitive adhesive composition according to the present invention has a special chemical structure of the aromatic petroleum resin, which is a tackifier,
It has an excellent balance of adhesive properties and has performance equivalent to or higher than that of products using natural resins. Further, in terms of heat resistance and weather resistance, it is expected that the performance will be superior to that of conventional products using aromatic petroleum resins.

Claims (2)

[Claims] 1. An aromatic petroleum resin having a chemical structure in which an aromatic ring is bonded via a methylene group, the bromination of which is 1.0 or less and the oxygen content is 1.0% by weight or less. An acrylic pressure-sensitive adhesive composition comprising: 2. The aromatic petroleum resin is a polymer obtained by reacting an aromatic compound or a fraction containing an aromatic compound as a main component with formaldehyde in the presence of an acid catalyst. The acrylic pressure-sensitive adhesive composition described.