difficulties, particularly at the dosing stage, but its popularity is growing and it is
becoming clear that it is complementary to masterbatch, rather than in
competition with it. It is widely considered best suited to long runs, where dosing
can be more controlled, but the latest equipment (such as Colortronic's new lowrate
gravimetric additive feeder, Graviblend S) is claimed to bring colour changes
down to seconds.
Recent development has concentrated on liquid colours for PET, to meet the
huge demand from the packaging sector. Ferro's SpectraFlo Type 99 is opaque,
complementing its range of transparent colours, meeting FDA rules and offering
a rapid colour change at a let-down ratio of 1000:1. A clear-tint PET green from
Milliken is said to have advantages over other liquid pigment dispersions for PET,
with cost savings over pre-coloured PET.
6.2 Addition of Colorants
Originally, pigments were dispersed in plastics simply by dry blending in a
tumble-mixer - or in an oil drum. The plasticizing function of an extruder or
injection moulding machine also offered a reasonably good method of dispersing
a pigment but the penetration of plastics into more critical markets brought
demands for greater homogeneity and consistency. To achieve best results,
however, pigmented compounds need to be prepared before moulding, using
dedicated equipment such as a compounding extruder, or pigments must be
formulated as concentrates, in a form giving trouble-free mixing with virgin
material alongside the moulding machine.
Concentrates or masterbatches are consistent, simple, and safe. They usually
come in a granular form, in which the concentrated pigment is dispersed in a
polymer carrier (such as polyethylene) that is compatible with the matrix resin.
The let-down ratio is usually 0.5-2%, depending on colour, host material, and
part thickness.
The advantages claimed include cost savings due to less handling, quick
colour changes, savings with lower inventory and reduced storage
requirements, no pollution from colour particles in the air, and easy and clean to
use. Colour dispersion is so good that precise measuring and mixing are not
essential (but good screw back-pressure is recommended), while there is no
adverse effect on the physical properties of the host material.
A typical range will cover around 400 colours, with a minimum order
quantity of 25 kg, but some suppliers can supply down to 1 kg at a surcharge.
Colour matching can also be done, usually on a minimum quantity of 50 kg.
There are around 200 producers of colour masterbatch, the leaders being Cabot,
Schulmann, Ampacet, andFerro.
Whether the colour is added by a specialist compounder or by a good technical
processor, the quality depends on dispersion and match. The pigment is dispersed
by 'wetting' the particles with the resin, and the size and shape of the particles
are therefore of great importance, as also are the rheological properties of the
resin matrix. Apart from colour fidelity, good dispersion also plays a role in
difficulties, particularly at the dosing stage, but its popularity is growing and it isbecoming clear that it is complementary to masterbatch, rather than incompetition with it. It is widely considered best suited to long runs, where dosingcan be more controlled, but the latest equipment (such as Colortronic's new lowrategravimetric additive feeder, Graviblend S) is claimed to bring colour changesdown to seconds.Recent development has concentrated on liquid colours for PET, to meet thehuge demand from the packaging sector. Ferro's SpectraFlo Type 99 is opaque,complementing its range of transparent colours, meeting FDA rules and offeringa rapid colour change at a let-down ratio of 1000:1. A clear-tint PET green fromMilliken is said to have advantages over other liquid pigment dispersions for PET,with cost savings over pre-coloured PET.6.2 Addition of ColorantsOriginally, pigments were dispersed in plastics simply by dry blending in atumble-mixer - or in an oil drum. The plasticizing function of an extruder orinjection moulding machine also offered a reasonably good method of dispersinga pigment but the penetration of plastics into more critical markets broughtdemands for greater homogeneity and consistency. To achieve best results,however, pigmented compounds need to be prepared before moulding, usingdedicated equipment such as a compounding extruder, or pigments must beformulated as concentrates, in a form giving trouble-free mixing with virgin同时注塑机的材料。精矿或色母粒是一致、 简单和安全。他们通常进来一个颗粒的形式,集中的颜料均匀分散在聚合物载体 (如聚乙烯) 与基体树脂相兼容。让人失望的比例往往是 0.5-2%,取决于主机材料的颜色和零件的厚度。声称的优势包括较少的处理成本节余快颜色的变化,储蓄与降低库存,减少存储要求,从颜色颗粒在空气中,无污染和简单和干净的使用。颜色色散很精确的测量和搅拌不是基本 (但建议好螺杆背压式),固然有没有对主机材料的物理性能的不利影响。一个典型的范围将涵盖大约 400 的颜色,带有一个最低限度的秩序25 公斤,而一些供应商的数量可以提供到附加费 1 公斤。颜色匹配也可以,通常 50 公斤的最低量。有大约 200 生产者色母,领导人被卡博特,舒尔,Ampacet,andFerro。由专家混合物或良好的技术是否添加颜色处理器,质量取决于分散和比赛。该色素被分散通过 '湿' 与树脂,以及大小和形状的粒子的粒子是因此极为重要,也是的流变性能树脂基体。除了色彩保真度,良好的分散性也起着作用
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