JPH032449B2

JPH032449B2 -

Info

Publication number: JPH032449B2
Application number: JP10230185A
Authority: JP
Inventors: Hitoshi Takahira; Kyoshi Saito; Juzo Akata; Norio Kawamoto
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 1985-05-14
Filing date: 1985-05-14
Publication date: 1991-01-16
Also published as: JPS61261371A

Description

[Detailed description of the invention]

〔産業上の利用分野〕本発明はエポキシ樹脂粉体組成物に関し、更に
詳しくはエポキシ樹脂とフエノール系硬化剤とを
含有して成るエポキシ樹脂粉体組成物に関する。〔従来の技術〕近年、粉体組成物たとえば粉体塗料は無公害、
省資源、省エネルギー型塗料として広い用途にわ
たつて従来の溶剤型塗料に置き換わりつつある。
ところが、一般的な粉体塗料は溶融時の粘度が高
いことから、一回の塗装操作で厚膜仕上げが出来
るという長所を持つ反面、被塗物との濡れ性、細
部への浸透性即ち間隙充填性、薄膜塗装性等に劣
るという欠点があり、また近年の用途拡大に伴つ
て上記欠点の改善と共に耐熱性や接着性の向上も
要望されるようになり、これ等に対処するため新
しい材料の開発が必要となつている。一方、エポキシ樹脂は液状から固形まで種々の
形態のものがあり、その種類と併用する硬化剤の
種類の選択によつて変化に富んだ硬化物物性を発
現出来ることから広範な分野で使用されている。
そしてこれ等エポキシ樹脂のうち上述した粉体塗
料に用いられるものとして、固形ビスフエノール
Ａ型、ビスフエノールＦ型、ノボラツク型等のエ
ポキシ樹脂が知られる。しかしながら、このような従来のエポキシ樹脂
は一般にある程度大きな分子量を有しているた
め、溶融粘度が高く、粉体塗料に用いた場合に既
述した被塗物との濡れ性、間隙充填性、薄膜塗装
性等に劣り、複雑な構造物の接着や狭い間隙への
充填には不適である。そこでこれ等の溶融粘度を
低下すべく分子量を小さくすることが考えられる
が、粉体塗料化が困難になる。また固形ビスフエ
ノールＡ型及びビスフエノールＦ型エポキシ樹脂
では官能基であるエポキシ樹脂間の鎖長が長いた
めに硬化物の架橋密度が低くなり、液状樹脂に比
較して耐熱性に劣る欠点があり、固形ノボラツク
型エポキシ樹脂では接着性が不充分である。尚、上記以外に低分子量で溶融粘度が低い常温
で固形のエポキシ樹脂としてトリスグリシジルイ
ソシアヌレートが知られるが、このものは接着力
が著しく低いという欠点がある。また液状のエポ
キシ樹脂を粉体塗料に用いる場合は、粉体化のた
めに半硬化させる必要があり、これによつて分子
量が増大して溶融粘度が高くなるという問題があ
る。また粉体塗料以外の粉体組成物たとえば接着
剤、成形材料の場合も上記と同様の問題点があつ
た。〔発明が解決しようとする問題点〕本発明者はエポキシ樹脂を粉体組成物として使
用する場合の上記問題点に注目し、これ等問題点
を解消するために従来から研究を続けて来たが、
この研究に於いて、エポキシ樹脂としてある特定
の結晶性エポキシ樹脂を使用する場合は、低い溶
融粘度を有し、間隙充填性に優れた粉体組成物が
得られることを見出し、これに基づく発明を完成
しすでに出願した。一方また本発明者はこの種エポキシ樹脂粉体組
成物就中その硬化剤について研究を続けている間
に、通常のエポキシ樹脂の硬化剤の一種であるフ
エノール系硬化剤を、上記の特定の結晶性エポキ
シ樹脂の硬化剤として使用した場合に、特にある
特定の２種類のフエノール系硬化剤を併用する場
合は、これ等両者の相乗作用により著しく吸湿性
が改善されることを見出した。またこれ等の併用
により、結晶性エポキシ樹脂を使用してこれを熱
硬化した際に、発泡や高温接着力低下を生じる傾
向があるという問題点も未然に解消出来ることを
見出した。本発明はこれ等の新しい事実に基づい
て完成されたものである。〔問題点を解決するための手段〕本発明は、結晶性エポキシ樹脂並びにフエノー
ル系硬化剤を含有して成る組成物であつて、上記
フエノール系硬化剤が、下記式(A) （但しＲは炭素数３以上のアルキル基）で示される基、及び下記式(B) （但しR′はＨまたはCH₃）で表わされる基を100対20〜100の割合で共に有し
て成るノボラツク型フエノール系樹脂硬化剤であ
ることを特徴とするエポキシ樹脂粉体組成物に係
るものである。〔作用〕本発明で使用する結晶性エポキシ樹脂は、融点
が50〜150℃である固体の結晶性エポキシ樹脂で
あり、従来この種分野で使用されて来た所謂結晶
性エポキシ樹脂が広く使用出来る。尚、ここで言
う結晶性エポキシ樹脂とは、Ｘ線回折により多数
の結晶のピークが表われる固形エポキシ樹脂であ
つて、物理的にはシヤープな融点を示し且つ溶融
時には分子間相互作用が殆んどなくなるため極端
に粘度が低下する性質を有する。特に本発明に於
いては、その融点よりも10℃高い温度での溶融粘
度が５ポイズ以下であるエポキシ樹脂が好まし
い。これ等の具体例としては、たとえば４，4′−
ビス（２，３エポキシプロポキシ）−３，3′，５，
5′−テトラメチルビフエニル、ジグリシジルテレ
フタレート、ジグリシジルハイドロキノン等を例
示出来る。更に詳しくは、たとえば下記一般式
（）で表わされるジグリシジルハイドロキノン
を代表例として説明すると、次の通りである。ジクリシジルハイドロキノンは式（）に於い
て繰り返し単位数ｎ＝０の化合物であり、結晶性
を有するものである。しかしながら本発明に於い
ては上記ｎが１〜５程度の化合物や、末端がエポ
キシ化されていない化合物を20％以下好ましくは
５％以下含んでいても良い。特に好ましい結晶性エポキシ樹脂は、下記構造
式（）（R″はＨ、CH₃またはハロゲン原子を示す）で示されるものである。このエポキシ樹脂に於い
てR″がCH₃の場合は融点は105℃で、これを溶融
した場合たとえば150℃で0.02ポイズ程度以上と
なる非常に低い粘度を示す。本発明に於いては該結晶性性エポキシ樹脂とし
ては上記で説明した通りその融点50〜150℃のも
のを使用するが、この際50℃に達しないものでは
目的物粉体組成物がプロツキングを生じ易く、ま
た逆に150℃よりも高くなると作業性が悪くなる
傾向がある。好ましい融点は80〜120℃程度であ
る。本発明において使用する硬化剤はノボラツク型
フエノール樹脂硬化剤であり、且つ該樹脂がその
分子中に、下記式(A) （但しＲは炭素数３以上のアルキル基）で表わされる基、並びに下記式(B) （但しR′はＨまたはCH₃）で表わされる基の両方を有するものが使用され
る。この際の基(A)と基(B)との割合は100対20〜100
好ましくは100対30〜80である。本発明の上記硬化剤に於いては、基(A)と基(B)と
が上記範囲であるかぎり、一つの樹脂に基(A)と基
(B)との両者が含まれている場合ばかりでなく、基
(A)を有する樹脂と基(B)を有する樹脂とを混合した
場合等も含まれ、要は硬化剤として所定量の基(A)
と(B)とが含まれていれば良い。代表的な本発明硬
化剤は、下記式（A′）（但しＲは上記に同じ）で表わされる化合物を出発原料としてノボラツク
型フエノール系樹脂（A′）と、下記式（B′）（R′は上記に同じ）で表わされる化合物を出発原料としたノボラツク
型フエノール系樹脂（B′）とを、基(A)と(B)とが
上記の所定範囲になるように、更に好ましくは該
樹脂（A′）100重量部に対し該樹脂（B′）20〜
100重量部特に好ましくは30〜80重量部の配合割
合で、混合して得たものである。本発明で使用するノボラツク型フエノール系樹
脂硬化剤は通常軟化点が70〜130℃程度で、また
粘度は１〜15ポイズ（150℃での溶融粘度）が好
ましい。この際粘度があまり低くなりすぎるとブ
ロツキングし易くなり、またあまり高くなりすぎ
ると流れ性が悪くなる傾向がある。この本発明硬化剤の使用割合は通常エポキシ樹
脂の有するエポキシ基１当量当たり硬化剤の官能
基0.5〜1.5当量程度である。本発明のエポキシ樹脂粉体組成物に於いては、
溶融粘度の調整、接着力改善等の目的でエポキシ
樹脂成分として前記結晶性エポキシ樹脂と共に必
要に応じてたとえばビスフエノールＡ型、ビスフ
エノールＦ型、ノボラツク型等の他のエポキシ樹
脂を併用することが出来る。但しこれ等の他のエ
ポキシ樹脂は使用目的に応じ全エポキシ樹脂成分
中50重量％以下の割合で使用することが出来る。また本発明では、硬化を促進させるために、使
用する硬化剤の種類に適合した硬化促進剤を粉体
組成物中に必要に応じて配合しても良い。このよ
うな硬化促進剤としては従来公知のものを使用出
来、たとえばイミダゾール、ジシアンジアミド、
イミダゾリン、ベンジルジメチルアミンなどの第
三級アミンなどが挙げられる。ここで使用する硬
化促進剤は硬化剤の種類や使用目的等によつても
変わるが、通常エポキシ樹脂100重量部に対し0.3
〜８重量部程度である。更に本発明組成物には、
従来からこの種粉末状エポキシ樹脂組成物に使用
されて来た各種の添加剤がいずれも使用出来、た
とえばタルク、ケイ砂、シリカ、炭酸カルシウ
ム、硫酸バリウムの如き充填剤、カーボンブラツ
ク、ベンガラ、酸化チタン、酸化クロム、シアニ
ンブルー、シアニングリーンの如き顔料、その他
流れ調整剤等を例示出来る。これ等添加剤の配合
割合は、その種類や用途に応じて変化するが、通
常0.5〜200重量％好ましくは0.5〜50重量％程度
である。本発明組成物は上記の各成分を乾式混合法や溶
融混合法などの既知の手段で混合し、粉砕及び分
級を行なつて得られる。この際の粘度としては、
30メツシユを通過する程度にするのが好ましい。かくして得られた本発明組成物は溶融時の粘度
が低く間隙充填性に優れ、被塗物に対する濡れ性
や薄膜塗装性もよく、硬化後は優れた耐熱性と接
着性を示すため、粉体塗料、成形材料、接着剤等
の広範な用途に好適に使用出来る。〔実施例〕以下に実施例を示して本発明をより具体的に説
明する。実施例１〜５後記第１表に示す所定の成分を所定割合で乾式
混合し、次いで粉砕し40メツシユの篩で分級して
エポキシ樹脂粉体組成物を得た。比較例１〜５実施例１〜５と同様にして組成物を調製した。上記各実施例及び比較例のエポキシ樹脂粉体組
成物について、150℃での溶融粘度、ゲル化時間、
間隙充填性、発泡、高温接着力を下記の方法で測
定した。その結果を第１表に併記した。上記各測
定方法は次の通りである。 (イ) 溶融粘度ブルツクフイールド粘度計で測定温度150℃、
ロータNo.21の条件で測定した。 (ロ) ゲル化時間試料粉末の0.1gを150±１℃に加熱したゲル
化時間測定用銅板に散布し針先で撹拌する。試
料粉末全部が溶融してから、針で撹拌が不可能
になるまでの時間をストツプウオツチで測定
し、ゲル化時間とした。 (ハ) 間隙充填率巾15mm、長さ100mm、厚さ1.0mmの２枚の鋼板
間に、厚さ0.5mmのスペーサーを２本を10mmの
間隔をおいて挟持し、鋼板を加熱して150℃に
至つた時点で両鋼板と両スペーサーとの間で構
成されたスリツト状の間隙に粉体組成物を振り
かけて、その溶融物を流し込み、その後180℃
で30分間保持して硬化させ、室温まで冷却後に
切断接着力を測定し、通常の室温下での剪断接
着力に対するこの方法による剪断接着力測定値
の比率（％）で示した。 (ニ) 発泡 180℃に加熱した鋼板に粉末3gを散布し、硬
化させ、硬化物の発泡の有無を調べた。 (ホ) 高温接着力 (ハ)で得られる剪断接着力試験片を150℃の雰
囲気で、剪断接着力測定した。 [Industrial Application Field] The present invention relates to an epoxy resin powder composition, and more particularly to an epoxy resin powder composition containing an epoxy resin and a phenolic curing agent. [Prior art] In recent years, powder compositions, such as powder coatings, have become pollution-free and
It is replacing conventional solvent-based paints in a wide range of applications as resource-saving and energy-saving paints.
However, since general powder coatings have a high viscosity when melted, they have the advantage of being able to create a thick film finish with a single coating operation, but they have poor wettability with the object being coated and poor penetration into fine details, i.e., gaps. It has drawbacks such as poor filling properties and thin film coating properties, and with the expansion of applications in recent years, improvements in heat resistance and adhesiveness have come to be required as well as improvements in the above drawbacks.To address these issues, new materials have been developed. There is a need for the development of On the other hand, epoxy resins come in various forms, from liquid to solid, and are used in a wide range of fields because they can exhibit a variety of physical properties of the cured product depending on the type and the type of curing agent used in combination. There is.
Among these epoxy resins, solid bisphenol A type, bisphenol F type, novolac type epoxy resins, etc. are known as those used in the above-mentioned powder coatings. However, since such conventional epoxy resins generally have a relatively large molecular weight, they have a high melt viscosity, and when used in powder coatings, they have poor wettability with the coated object, gap filling properties, and thin film. It has poor paintability and is unsuitable for adhering complex structures or filling narrow gaps. Therefore, reducing the molecular weight in order to lower the melt viscosity of these materials is considered, but it becomes difficult to make them into powder coatings. In addition, solid bisphenol A type and bisphenol F type epoxy resins have a long chain length between the epoxy resins that are functional groups, resulting in a low crosslinking density of the cured product, which has the disadvantage of inferior heat resistance compared to liquid resins. , solid novolak type epoxy resins have insufficient adhesion. In addition to the above, trisglycidyl isocyanurate is known as an epoxy resin with a low molecular weight and low melt viscosity that is solid at room temperature, but this resin has the drawback of extremely low adhesive strength. Furthermore, when a liquid epoxy resin is used in a powder coating, it is necessary to semi-cure it to make it into a powder, which poses a problem in that the molecular weight increases and the melt viscosity increases. Further, problems similar to those described above also occur in the case of powder compositions other than powder coatings, such as adhesives and molding materials. [Problems to be solved by the invention] The present inventor has focused on the above-mentioned problems when using an epoxy resin as a powder composition, and has continued research to solve these problems. but,
In this research, we discovered that when a certain crystalline epoxy resin is used as the epoxy resin, a powder composition with low melt viscosity and excellent gap filling properties can be obtained, and we have developed an invention based on this. has been completed and has already been submitted. On the other hand, while continuing research into this type of epoxy resin powder composition, especially its curing agent, the present inventor used a phenolic curing agent, which is a type of curing agent for ordinary epoxy resins, in the above-mentioned specific crystals. It has been found that when used as a curing agent for epoxy resins, particularly when two specific types of phenolic curing agents are used together, the synergistic effect of these two types significantly improves hygroscopicity. It has also been found that by using these in combination, it is possible to eliminate the problem that when a crystalline epoxy resin is used and thermally cured, it tends to cause foaming and a decrease in high-temperature adhesive strength. The present invention was completed based on these new facts. [Means for Solving the Problems] The present invention provides a composition comprising a crystalline epoxy resin and a phenolic curing agent, wherein the phenolic curing agent has the following formula (A): (However, R is an alkyl group having 3 or more carbon atoms) and the following formula (B) (wherein R' is H or CH ₃ ) An epoxy resin powder composition characterized in that it is a novolak-type phenolic resin curing agent comprising both groups represented by the formula (R' is H or CH 3 ) in a ratio of 100:20 to 100. It is something. [Function] The crystalline epoxy resin used in the present invention is a solid crystalline epoxy resin with a melting point of 50 to 150°C, and so-called crystalline epoxy resins that have been conventionally used in this type of field can be widely used. . The crystalline epoxy resin referred to here is a solid epoxy resin that shows many crystal peaks in X-ray diffraction, and physically shows a sharp melting point and has almost no intermolecular interaction when melted. It has the property of extremely decreasing viscosity as it disappears. Particularly in the present invention, an epoxy resin having a melt viscosity of 5 poise or less at a temperature 10° C. higher than its melting point is preferred. Specific examples of these include, for example, 4,4'-
Bis(2,3 epoxypropoxy)-3,3',5,
Examples include 5'-tetramethylbiphenyl, diglycidyl terephthalate, and diglycidyl hydroquinone. More specifically, diglycidyl hydroquinone represented by the following general formula () will be explained as a representative example as follows. Diclycidylhydroquinone is a compound of the formula () in which the number of repeating units n=0, and has crystallinity. However, in the present invention, the composition may contain 20% or less, preferably 5% or less, of a compound where n is about 1 to 5 or a compound whose terminal is not epoxidized. A particularly preferable crystalline epoxy resin has the following structural formula () (R″ represents H, CH ₃ or a halogen atom.) If R″ is CH ₃ in this epoxy resin, the melting point is 105°C, and when it is melted, it will melt at 150°C, for example. It has a very low viscosity of about 0.02 poise or more. In the present invention, as the crystalline epoxy resin, one with a melting point of 50 to 150°C is used as explained above, but in this case, if the melting point does not reach 50°C, the target powder composition will not block. This tends to occur, and conversely, when the temperature is higher than 150°C, workability tends to deteriorate. The preferred melting point is about 80 to 120°C. The curing agent used in the present invention is a novolac type phenolic resin curing agent, and the resin has the following formula (A) in its molecule. (However, R is an alkyl group having 3 or more carbon atoms) and the following formula (B) (However, R' is H or CH ₃ ) Those having both groups are used. In this case, the ratio of group (A) to group (B) is 100:20 to 100.
Preferably the ratio is 30 to 80 to 100. In the above-mentioned curing agent of the present invention, as long as the groups (A) and (B) are within the above range, the group (A) and the group (B) can be combined in one resin.
(B) and the basic
This also includes cases where a resin having (A) and a resin having a group (B) are mixed, and the point is that a predetermined amount of the group (A) is used as a curing agent.
It is sufficient if it includes and (B). A typical curing agent of the present invention has the following formula (A') (However, R is the same as above) Novolac type phenolic resin (A') and the following formula (B') are prepared using the compound represented by as starting material. (R' is the same as above) A novolak-type phenolic resin (B') starting from a compound represented by (R' is the same as above) is more preferably added so that the groups (A) and (B) are within the above specified range. is 20 to 100 parts by weight of the resin (B') to 100 parts by weight of the resin (A').
It is obtained by mixing at a blending ratio of 100 parts by weight, particularly preferably 30 to 80 parts by weight. The novolak type phenolic resin curing agent used in the present invention usually has a softening point of about 70 to 130°C, and preferably has a viscosity of 1 to 15 poise (melt viscosity at 150°C). At this time, if the viscosity becomes too low, blocking tends to occur, and if the viscosity becomes too high, flowability tends to deteriorate. The ratio of the curing agent of the present invention used is usually about 0.5 to 1.5 equivalents of the functional group of the curing agent per equivalent of epoxy group contained in the epoxy resin. In the epoxy resin powder composition of the present invention,
For the purpose of adjusting melt viscosity, improving adhesive strength, etc., other epoxy resins such as bisphenol A type, bisphenol F type, novolak type, etc. may be used in combination with the crystalline epoxy resin as an epoxy resin component, if necessary. I can do it. However, these other epoxy resins can be used in an amount of up to 50% by weight of the total epoxy resin component depending on the purpose of use. Further, in the present invention, in order to accelerate curing, a curing accelerator suitable for the type of curing agent used may be blended into the powder composition as necessary. Conventionally known curing accelerators can be used, such as imidazole, dicyandiamide,
Examples include tertiary amines such as imidazoline and benzyldimethylamine. The curing accelerator used here varies depending on the type of curing agent and the purpose of use, but it is usually 0.3 parts by weight per 100 parts by weight of the epoxy resin.
~8 parts by weight. Furthermore, the composition of the present invention includes:
Any of the various additives conventionally used in powdered epoxy resin compositions of this type can be used, including fillers such as talc, silica sand, silica, calcium carbonate, barium sulfate, carbon black, red iron, and oxidation. Examples include titanium, chromium oxide, pigments such as cyanine blue and cyanine green, and other flow control agents. The blending ratio of these additives varies depending on their type and use, but is usually about 0.5 to 200% by weight, preferably about 0.5 to 50% by weight. The composition of the present invention can be obtained by mixing the above-mentioned components by a known method such as a dry mixing method or a melt mixing method, followed by pulverization and classification. The viscosity at this time is
It is preferable to set it to the extent that it passes through 30 meshes. The thus obtained composition of the present invention has a low viscosity when melted, excellent gap-filling properties, good wettability and thin film coating properties on objects to be coated, and exhibits excellent heat resistance and adhesive properties after curing, so it can be used as a powder. It can be suitably used in a wide range of applications such as paints, molding materials, and adhesives. [Example] The present invention will be described in more detail with reference to Examples below. Examples 1 to 5 Predetermined components shown in Table 1 below were dry mixed in a predetermined ratio, then ground and classified using a 40 mesh sieve to obtain an epoxy resin powder composition. Comparative Examples 1-5 Compositions were prepared in the same manner as Examples 1-5. Regarding the epoxy resin powder compositions of each of the above Examples and Comparative Examples, the melt viscosity at 150°C, gelation time,
Gap filling properties, foaming, and high temperature adhesive strength were measured by the following methods. The results are also listed in Table 1. The above measurement methods are as follows. (a) Melt viscosity Measured using a Burckfield viscometer at a temperature of 150°C.
Measured under the conditions of rotor No. 21. (b) Gel time Sprinkle 0.1 g of the sample powder onto a copper plate for measuring gel time heated to 150±1°C and stir with the tip of a needle. The time from when all the sample powder was melted until it became impossible to stir with a needle was measured with a stopwatch, and this was taken as the gelation time. (c) Gap filling ratio Two 0.5 mm thick spacers are sandwiched between two steel plates with a width of 15 mm, a length of 100 mm, and a thickness of 1.0 mm, with a gap of 10 mm between them, and the steel plates are heated to 150 mm. Once the temperature reaches 180°C, the powder composition is sprinkled into the slit-shaped gap formed between both steel plates and both spacers, and the molten material is poured in.
The adhesive was held for 30 minutes to cure, and after cooling to room temperature, the cutting adhesive strength was measured and expressed as the ratio (%) of the shear adhesive strength measured by this method to the normal shear adhesive strength at room temperature. (iv) Foaming 3 g of powder was sprinkled on a steel plate heated to 180°C, allowed to harden, and the presence or absence of foaming in the cured product was examined. (e) High-temperature adhesive strength The shear adhesive strength of the shear adhesive strength test piece obtained in (c) was measured in an atmosphere at 150°C.

【表】但し上記第１表で使用したエポキシ樹脂−
（）、並びにエポキシ樹脂−（）は夫々次のも
のである。〔効果〕上記第１表からも明らかな通り本発明組成物は
間隙充填製に優れると共に発泡性並びにタレの点
についても極めて優れている。また第１表には特に示していないが、吸湿性に
極めて優れたものである。[Table] However, the epoxy resin used in Table 1 above-
() and epoxy resin-() are as follows, respectively. [Effects] As is clear from Table 1 above, the composition of the present invention is excellent in gap-filling properties and is also extremely excellent in terms of foamability and sagging. Although not particularly shown in Table 1, it has extremely excellent hygroscopicity.

Claims

[Scope of Claims] 1. A composition comprising a crystalline epoxy resin and a phenolic curing agent, wherein the phenolic curing agent has the following formula: (However, R is an alkyl group having 3 or more carbon atoms) A novolak type phenolic resin curing agent (A') using a compound represented by the following as a starting material and the following formula (wherein R' is H or CH ₃ ) An epoxy resin powder composition characterized in that it contains a novolak type phenolic resin curing agent (B') using a compound represented by R' as a starting material. . 2 The above phenolic resin curing agent (B') is 20 to 100 parts by weight per 100 parts by weight of the above phenolic resin curing agent.
A powder composition according to claim 1, comprising parts by weight. 3 Crystalline epoxy resin is 4,4′-bis(2″,
The powder composition according to claim 1 or 2, which is 3''-epoxybropoxy)-3,3',5,5'-tetramethylbiphenyl.