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報 文
LPAの分散粒子径と均一着色性の相関性野中 眞一,濱田 健一,殿谷 秀二,山田 寿一
The Relationship between the Diameter of Dispersed LPA Particles and
Color Uniformity
Nonaka Shin-ichi, Hamada Ken-ichi, Tonogai Shuji and Yamada Hirokazu
One of the common defects in bulk molding compound (BMC) parts is mottling, which makes it
di�cult to mold deep-colored BMC parts. However, the detailed cause of the defect is still unknown.
In this paper, the relationship between color uniformity in BMC parts and the dispersed particle
size of the Low Pro�le Additive (LPA) was studied. Mottling of cast parts, which were composed
of unsaturated polyester resin (UP), LPA, deep-color pigment and catalyst, were observed with an
electron microscope. It was observed that there were large LPA particles containing large voids in
light-color parts and small LPA particles with small voids in deep-colored parts. It was assumed
that the control of the dispersed particle size of LPA and formed voids could allow BMC parts of
deep uniform color. Addition of a lightly cross-linked polystyrene (LCPSt), with a particle size of
5-30 micrometer (�m), reduced the dispersed particle size of LPA and narrowed the distribution of
the LPA particle size. Consequently, the color uniformity improved. By controlling the dispersed
particle size of LPA, mottling in BMC parts could be reduced, and the applications and market of
BMC and SMC expanded.
1 緒言低収縮化剤 (LPA) は BMC(Bulk Molding Com-
pound)の寸法安定性を維持する上で必要不可欠であ
る。しかし,現在,一般的に用いられている LPAの
中にはTable 11)に示すように,低収縮化効果と,特に
濃色領域の着色性を両立させるものは見つかっていな
い。M. C. Kastlら2)や K. E. Atkinsら3)は低収縮化
効果の高いポリ酢酸ビニル (PVAc)の着色性改良を報
告しているが,色ムラについての考慮はされていない。
色ムラの発現要因としては,顔料の分散性,不飽和
ポリエステル樹脂 (UP) の種類,LPA との組み合わ
せなどがあり,不確定要素が多くなり煩雑となる。本
研究では,UP,LPA,顔料,硬化剤を固定して検討
し,色ムラの原因解明,LPA 分散粒子径と色ムラの
関係を明確化するとともに,成形材料のための新たな
LPA分散技術を提案する。
Table 1 Properties of Conventional LPAs
PMMA PSt PVAc PB*
Shrinkage Good Fair Excellent Poor
Pigmentability Fair Good Poor Fair
Paintabilities Fair Poor Good Good
Physical Good Fair Poor FairProperties
Water Fair Fair Poor GoodResistance
*Polybutadiene
2 実験2.1 色ムラ確認のための注型板作成UP(無水マレイン酸/プロピレングリコール)80g
に対し,低収縮化剤としてポリスチレン (PSt)の 51%
スチレン溶液 20g,青顔料を 3g,tert-ブチルパーベン
ゾエート (TBPB)を硬化剤として 1g添加し,1分間混
合攪拌し,1333 Pa下,1分間減圧脱泡し,直径 20cm
の円盤型に注ぐ。120�Cにて 2時間で硬化させる。
低架橋ポリスチレン (LCPSt)添加系も,該粉末を
Table 2に従い配合し,同条件下で硬化させる。
2.2 色ムラ確認のためのBMC作成およびその成形方法
Table 3の配合に従い,順に添加,混合する。得ら
れた混合物を 45�Cで 24時間熟成し,粘着性のない
Table 2 Casting Formulation for Measurement of
Non-uniform Coloration
Casting-1 Casting-2 Casting-3
UP 80 80 80
LCPSt 5 20
PSt 20 20 20
(51% in SM)
Pigment 0.5 0.5 0.5
(Blue)
TBPB 1 1 1
Unit: phr
DIC Technical Review No.5/1999 39
報 文
Table 3 Formulation of BMC
BMC-1 BMC-2 BMC-3 BMC-4
UP 80 80 80 80
Inhibitor 0.8 0.8 0.8 0.8
LCPSt 20
PSt 20 20(51% in SM) PMMA 20 (40% in SM) Pigment 1 1 1 1(Blue)