JP4591732B2 - Recyclable adhesive tape - Google Patents

Description

【００２４】
【表２】

【００２５】
＜粘着テープ＞
アプリケーターを用い、粘着剤組成物を、乾燥後の厚さが３０μｍとなるようにセパレータ上に塗布し、８０℃で３分間乾燥した後、表３に記載の基材Ａ〜Ｄの両面に貼り合わせ、実施例１〜６、および比較例１〜３の両面粘着テープを作製した。
【００２６】
【表３】

【００２７】
＜粘着テープの試験および結果の評価＞
実施例１〜６、および比較例１〜３の粘着テープについて、接着力、再剥離性、および溶融リサイクル適性を、下記の方法で試験し、評価した。
【００２８】
〔接着力〕
２０ｍｍ幅×１００ｍｍ長さの２３μｍのＰＥＴフィルムで片面をバッキングした粘着テープを２３℃にてポリスチレン板に貼付し、２ｋｇローラーで１往復加圧した。３０分間放置後、２３℃にて１８０°方向に３００ｍｍ／ｍｉｎで剥離し、接着力を測定した。結果を表５に示す。
【００２９】
〔再剥離性〕
２３℃にて２５ｍｍ幅×１００ｍｍ長さの粘着フィルムをポリスチレン板およびステンレス板に貼付し、６０℃９０％ＲＨで５日間の条件で放置後、１３５°方向に５〜１０ｍ／ｍｉｎの速度で引き剥がしたときのテープのチギレおよび粘着剤の糊残りを観察し、両面粘着テープのＭＤ方向とＴＤ方向で評価した。評価結果を表５に示す。
再剥離性の評価基準は以下の通り。
◎：糊残り、および粘着テープのチギレがなく、ポリスチレン板およびステンレス板とも再剥離可能。
○：剥離きっかけ部に一部糊残りするが、ポリスチレン板およびステンレス板とも再剥離可能。
×：ポリスチレン板あるいはステンレス板に対し、全面糊残りまたは粘着テープのチギレがあり、再剥離不可能。
【００３０】
〔溶融リサイクル適性〕
ＨＩＰＳｔ樹脂（大日本インキ化学工業製「ＧＨ−８３００−１」）に、実施例１〜６、および比較例１〜３の粘着テープを５質量％の割合で混合し、再ペレット化したものを射出成型器で成型し、試験サンプルとした。「ＧＨ−８３００−１」のみの成型品を標準サンプルとし、各試験サンプルの機械的特性（引張強度、引張伸び）を測定した。引張強度［ＭＰａ］、および引張伸び［伸び％］は、いずれもＪＩＳ Ｋ６８７１に従い、引張速度５ｍｍ／ｍｉｎで測定した。測定結果を表４に、評価結果を表５に示す。
溶融リサイクル適性の評価基準は以下の通り。
標準サンプルの測定値を１００としたとき、標準サンプルと各試験サンプルの測定値の差（ΔＶ）が、
◎：両項目とも ０≦ΔＶ＜５の場合。
△：どちらか１項目が ０≦ΔＶ＜５、他項目が５≦ΔＶ＜１０ 、または両項目とも ５≦ΔＶ＜１０の場合。
×：少なくともどちらか１項目が １０≦ΔＶ の場合。
【００３１】
【表４】

【００３２】
【表５】

【００３３】
表５に記載した結果から明らかなように、実施例はいずれも高い接着力を示しており、かつ再剥離性、溶融リサイクル適性の両面に優れている。
【発明の効果】
本発明の粘着テープは、構成する支持体フィルムおよび粘着剤がともにＰＳｔおよび／またはＡＢＳに相溶する。被着体がＰＳｔまたはＡＢＳの樹脂成型部品である場合は、該粘着テープを貼着したまま、機械的特性を損なうことなく溶融リサイクルすることができる。被着体が上記樹脂以外の場合は、リサイクルに際して剥離する必要があるが、本発明の粘着テープに使用する支持体フィルムは、ＭＤ方向とＴＤ方向に強い引張強度を有しており、また粘着剤は分解劣化しにくい特徴を有するので、高い接着力を持ちながら、糊残りやチギレを起こすことなく容易に剥離することができ、加熱処理あるいは溶剤処理等の、従来剥離のために必要とされた特殊な工程が不要であるという、顕著な効果を発現する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure-sensitive adhesive tape for fixing a melt-recyclable resin molded part. Specifically, polystyrene (hereinafter abbreviated as PSt) and acrylonitrile-butadiene-styrene (hereinafter abbreviated as ABS) resin molded parts can be melt-recycled without removing the tape, and the adherend is resin molded other than the above. In the case of components, the present invention relates to an adhesive tape that can be peeled off from the adherend without any adhesive residue or tears without performing special peeling treatment such as heat treatment or solvent treatment. (Hereinafter, the ability to peel off without adhesive residue or scratches is called re-peeling, and the ability to re-peel is called re-peeling.)
[0002]
[Prior art]
As part of environmental measures in recent years, thermoplastic resins such as PSt, ABS, polycarbonate / acrylonitrile-butadiene-styrene (hereinafter abbreviated as PC / ABS) that can be melt-recycled have been adopted for resin molded parts such as electronic devices. Yes.
When fixing these thermoplastic resin molded parts, there are a method of using an adhesive and a welding method, but an adhesive tape is frequently used because of good workability and workability. In particular, the fixing with the double-sided adhesive tape is advantageous when the shape of the component to be fixed is complicated or when productivity in an automated line is required.
[0003]
Conventionally, when recycling resin molded parts fixed with these adhesive tapes, it was common to melt and recycle after peeling the attached adhesive tape. A time-consuming process such as softening, physically cutting, or scraping the adhesive was required. JP-A-8-209086 discloses a pressure-sensitive adhesive tape that exhibits a strong adhesive force when a resin molded part is fixed and has no adhesive residue or tear when peeled.
[0004]
On the other hand, methods for melting and recycling resin molded parts with an adhesive tape attached are disclosed in Japanese Patent Application Laid-Open Nos. 4-136082 and 7-3218. This method can be used in the case of a combination in which the adherend and the adhesive tape are compatible with each other, but is not necessarily used only in such a specific combination. In the case of a combination that is not compatible with each other, it will have to be peeled off as before, but until now, no adhesive tape that can be melt-recycled while being stuck and has removability at the same time is not known .
[0005]
Japanese Patent Application Laid-Open No. 8-34088 also discloses an electronic device component that can be melt-recycled with a sheet-like member attached, and the adherend and the sheet are used as an adhesive between the adherend and the sheet-like member. Only PMMA having compatibility with the shaped member is illustrated, and there is no description or suggestion about a specific configuration as an adhesive tape, re-peelability, or the like.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and the problem is that it can be melt-recycled while sticking to a specific resin molded part, and for other resin molded parts. It is an object of the present invention to provide a so-called re-peelable pressure-sensitive adhesive tape that exhibits a strong adhesive force for a long period of time when fixed, and has no tear or adhesive residue when peeled.
In the case of melting and recycling with an adhesive tape attached to a resin molded part, it is not sufficient that the adherend resin and the adhesive tape are merely compatible. It is also an issue to suppress the fluctuation between the mechanical characteristics of the recycled resin molded part melted and recycled and the mechanical characteristics of the genuine resin molded part as small as possible.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have completed the present invention.
That is, the pressure-sensitive adhesive tape of the present invention has compatibility with PSt and / or ABS, which is frequently used as a thermoplastic resin for resin molded parts, can be melt-recycled while being stuck to the resin molded parts, and For resin molded parts other than the thermoplastic resin, the adhesive tape has good removability. The structure is compatible with PSt, ABS, PC / ABS, and has a tensile strength of 20 N / 20 mm or more in the flow direction (hereinafter abbreviated as MD) and the width direction (hereinafter abbreviated as TD). An adhesive layer containing a styrene block copolymer and a tackifying resin is provided on at least one surface of the body film.
The adhesive tape of the present invention is compatible with adherend resins other than PSt and ABS, and the mechanical properties of the recycled resin molded product are compared with those of genuine resin molded parts. If it does not fluctuate greatly, it can be melted and recycled with it attached.
[0008]
In order to solve the above-mentioned problems, in the present invention, a styrene block copolymer having compatibility with PSt and ABS is used as the main component of the pressure-sensitive adhesive. Among these, styrene-isoprene-styrene block copolymer (hereinafter abbreviated as SIS) is preferable. In addition, as a tackifying resin to be added to the pressure-sensitive adhesive for imparting sufficient adhesive force, a known and commonly used resin can be used. Particularly, a rosin resin having a hydroxyl value of 15 or more and 100 or less is used for microphase separation. It is easy to make it preferable.
[0009]
However, it is described in the following document 1 that the rosin resin easily generates free radicals by oxygen in the air, and the free radicals decompose and degrade the adhesive.
Reference 1: Toyama et al., Japan Adhesion Association, Vol. 9, no. 3,120 (1973)
In the SIS-rosin resin system of the present invention, the present inventors also have degradation degradation due to cleavage of the double bond of the main chain of SIS, and the degradation degradation as the hydroxyl value of the rosin resin increases. I found it easy to do. When SIS degrades and degrades, the cohesive force of the pressure-sensitive adhesive decreases, resulting in a decrease in adhesive strength and a cause of adhesive residue at the time of peeling. For this reason, the crosslinking agent is preferably one that can appropriately control the amount of hydroxyl groups in the rosin resin that causes degradation. For this purpose, an isocyanate-based crosslinking agent that undergoes a crosslinking reaction with a hydroxyl group is suitable.
[0010]
In addition, the present inventors can use the amount of oxygen absorbed within a certain time under a certain condition of the resin solution described in the above-mentioned document 1 as an index of the ease of decomposition and degradation of the pressure-sensitive adhesive by the tackifier resin. I found. As a result, the oxygen absorption amount of the tackifying resin used for the pressure-sensitive adhesive of the present invention is preferably 1 ml or less.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in further detail below.
The support film of the present invention is compatible with PSt and / or ABS at the time of melting, and has a tensile strength of 20 N / 20 mm or more in the MD and TD directions in order not to cause tearing at the time of re-peeling. It is not particularly limited. Specific examples include a PSt film, a high impact polystyrene (hereinafter abbreviated as HIPSt) film, a biaxially stretched polystyrene (hereinafter abbreviated as OPSt) film, and an ABS film. The thickness of the film is preferably 5 to 200 μm. Moreover, in order to improve adhesiveness with an adhesive, you may perform a corona treatment and a primer process to the support body film surface.
[0012]
In the present invention, the tensile strength of the support film was measured using a sample punched into a dumbbell shape having a marked line length of 100 mm and a width of 20 mm, using a Tensilon tensile tester at 23 ° C. under a tensile speed of 300 mm / min. .
[0013]
Examples of the styrenic block copolymer of the present invention include block copolymers such as SIS, styrene-butadiene-styrene (hereinafter abbreviated as SBS), and styrene-ethylenepropylene-styrene. The molecular weight is preferably 10,000 to 800,000. If it is less than 10,000, the cohesive force of the pressure-sensitive adhesive is low, and if it exceeds 800,000, sufficient adhesive force cannot be obtained. The diblock amount is preferably 30 to 80% by mass or less. If it is less than 30% by mass, sufficient adhesion cannot be obtained, and if it exceeds 80% by mass, sufficient holding force cannot be obtained.
[0014]
Examples of the tackifying resin of the present invention include C5 petroleum resins, alicyclic petroleum resins, alicyclic / aromatic petroleum resins, terpene resins, rosin resins, rosin ester resins, terpene-phenol resins, alkylphenols. Examples thereof include resins. The addition amount is preferably 60 to 200% by mass with respect to the styrenic block copolymer. When the amount is less than 60% by mass, sufficient adhesive strength cannot be obtained, and when it exceeds 200% by mass, the heat resistant holding force decreases.
In the case of a rosin resin, the preferred range of the hydroxyl value is 15-100. In the system with SIS, the higher the hydroxyl value of the rosin resin, the easier the microphase separation occurs. However, when it exceeds 100, the above-described degradation of SIS is promoted. It becomes sufficient, and the viscosity of the pressure-sensitive adhesive does not increase, so that a sufficient curved surface adhesive force cannot be obtained.
[0015]
As described above, the smaller the oxygen absorption amount of the tackifying resin, the more the degradation and degradation of the pressure-sensitive adhesive are suppressed. The oxygen absorption amount is most preferably 0, but the usually preferable range is 0.01 to 1 ml. In addition, the oxygen absorption amount of the tackifying resin was measured according to the method described in the above-mentioned literature 1, using a high-pressure oxygen absorption measuring apparatus of Bolund, dissolving 10 g of the tackifying resin in 10 ml of o-dichlorobenzene, The amount of oxygen absorbed when left for 15 minutes was determined as an oxygen pressure of 760 mmHg and a volume of 25 ° C.
[0016]
As the crosslinking agent of the present invention, known and commonly used polyisocyanates, melamine resins, urea resins, epoxy resins, metal chelates, metal oxides, metal salts, metal hydroxides, acid anhydrides, polyamines and the like can be used. Among these, it is particularly preferable to use an isocyanate-based crosslinking agent having reactivity with a hydroxyl group. In order to obtain a good balance between the viscosity of the pressure-sensitive adhesive and the amount of residual hydroxyl group after the crosslinking reaction, it is preferable that the molar equivalent of the isocyanate group with respect to the hydroxyl group of the tackifier resin is 0.1 to 10. .
[0017]
Various known and conventional additives such as antioxidants, ultraviolet absorbers, fillers, pigments, thickeners and the like can be added to the pressure-sensitive adhesive layer as long as the adhesive strength is not impaired.
[0018]
The styrenic block copolymer, tackifying resin, cross-linking agent, and various additives may be used in a known or commonly used solvent, for example, toluene, ethyl acetate, n-hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, tetrahydrofuran or the like alone or in a mixed solvent. The pressure-sensitive adhesive composition having a solid content of 10 to 80% by mass is prepared by dissolving or dispersing in the solution.
[0019]
The pressure-sensitive adhesive layer can be formed on the support film by a method generally used for coating an adhesive tape. The pressure-sensitive adhesive composition may be directly applied to the support film and dried, but it is preferable that the pressure-sensitive adhesive composition is once applied to the separator, dried and then bonded to the support film.
[0020]
The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, but is preferably 5 to 400 μm, which is about the same as a general pressure-sensitive adhesive tape.
[0021]
【Example】
Hereinafter, the present invention will be described more specifically by describing examples and comparative examples of the present invention. However, the present invention is not limited to this. Further, “parts” and “%” mean “parts by mass” and “mass%”, respectively, unless otherwise specified.
[0022]
<Adhesive composition>
Styrenic block copolymer, acrylic polymer, tackifying resin listed in Table 1, antioxidant, and crosslinking agent are blended in the proportions listed in Table 2, dissolved in toluene, and a solids concentration of 50%. Compositions I-VI were prepared.
In Table 2, Irganox NC-4 is an antioxidant and Vernox NC-40 is an isocyanate crosslinking agent.
[0023]
[Table 1]

[0024]
[Table 2]

[0025]
<Adhesive tape>
Using an applicator, the pressure-sensitive adhesive composition was applied onto the separator so that the thickness after drying was 30 μm, dried at 80 ° C. for 3 minutes, and then applied to both surfaces of the substrates A to D described in Table 3 In addition, double-sided pressure-sensitive adhesive tapes of Examples 1 to 6 and Comparative Examples 1 to 3 were produced.
[0026]
[Table 3]

[0027]
<Test of adhesive tape and evaluation of results>
For the pressure-sensitive adhesive tapes of Examples 1 to 6 and Comparative Examples 1 to 3, adhesive strength, removability, and melt recyclability were tested and evaluated by the following methods.
[0028]
[Adhesive strength]
A pressure-sensitive adhesive tape, one side of which was backed up with a 20 mm wide × 100 mm long 23 μm PET film, was attached to a polystyrene plate at 23 ° C., and pressed once with a 2 kg roller. After standing for 30 minutes, the film was peeled off at 300 mm / min in the 180 ° direction at 23 ° C., and the adhesive strength was measured. The results are shown in Table 5.
[0029]
[Removability]
An adhesive film with a width of 25 mm × 100 mm at 23 ° C. was attached to a polystyrene plate and a stainless steel plate, left at 60 ° C. and 90% RH for 5 days, and then pulled at a speed of 5 to 10 m / min in the 135 ° direction. The tape was peeled off when peeled and the adhesive residue of the adhesive was observed, and evaluated in the MD direction and TD direction of the double-sided adhesive tape. The evaluation results are shown in Table 5.
The evaluation criteria for removability are as follows.
A: There is no adhesive residue and no adhesive tape, and it can be re-peeled from polystyrene plates and stainless steel plates.
○: Part of the adhesive remains on the peeling trigger part, but can be removed again from the polystyrene plate and the stainless steel plate.
X: The entire surface of the polystyrene plate or stainless steel plate has adhesive residue or adhesive tape that cannot be removed again.
[0030]
[Melting recycling suitability]
HIPSt resin ("GH-8300-1" manufactured by Dainippon Ink & Chemicals, Inc.) was mixed with the adhesive tapes of Examples 1 to 6 and Comparative Examples 1 to 3 at a ratio of 5% by mass and re-pelletized. Molded with an injection molding machine and used as a test sample. The molded product of only “GH-8300-1” was used as a standard sample, and the mechanical properties (tensile strength and tensile elongation) of each test sample were measured. Tensile strength [MPa] and tensile elongation [elongation%] were both measured according to JIS K6871 at a tensile speed of 5 mm / min. The measurement results are shown in Table 4, and the evaluation results are shown in Table 5.
The evaluation criteria for melt recycling suitability are as follows.
When the measured value of the standard sample is 100, the difference (ΔV) between the measured value of the standard sample and each test sample is
A: Both items are 0 ≦ ΔV <5.
Δ: Either one item is 0 ≦ ΔV <5, the other item is 5 ≦ ΔV <10, or both items are 5 ≦ ΔV <10.
×: When at least one of the items is 10 ≦ ΔV.
[0031]
[Table 4]

[0032]
[Table 5]

[0033]
As is clear from the results described in Table 5, all of the examples show high adhesive strength, and are excellent in both removability and melt recyclability.
【The invention's effect】
In the pressure-sensitive adhesive tape of the present invention, the constituting support film and the pressure-sensitive adhesive are both compatible with PSt and / or ABS. When the adherend is a molded resin part of PSt or ABS, it can be melt-recycled without damaging the mechanical properties while the adhesive tape is stuck. When the adherend is other than the above-mentioned resin, it is necessary to peel off when recycling. However, the support film used for the adhesive tape of the present invention has a strong tensile strength in the MD direction and the TD direction, and is also adhesive. Since the agent has the feature that it is difficult to decompose and degrade, it can be easily peeled off without causing adhesive residue or tearing while having high adhesive strength, and is required for conventional peeling such as heat treatment or solvent treatment. This produces a remarkable effect that no special process is required.

Claims (3)

A pressure-sensitive adhesive tape having a polystyrene resin and / or acrylonitrile-butadiene-styrene resin molded part as an adherend, compatible with the resin, and melt-recyclable while attached to the adherend. Flow direction and width Having a pressure-sensitive adhesive layer containing a styrene-based block copolymer and a rosin-based resin having a hydroxyl value of 15 or more and 100 or less on at least one surface of a support film having a tensile strength of 20 N / 20 mm or more in each direction;
The support film is a film made of polystyrene, high impact polystyrene, biaxially stretched polystyrene or acrylonitrile-butadiene-styrene,
The pressure-sensitive adhesive tape, wherein the pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent.   The pressure-sensitive adhesive tape according to claim 1, wherein the styrenic block copolymer is a styrene-isoprene-styrene block copolymer. The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the oxygen-absorbing amount of the tackifying resin is 1 ml or less.