DD210698A1 - METHOD FOR STABILIZING PIGMENTSUSPENSIONS - Google Patents

Abstract

The invention relates to a process for the stabilization of pigment suspensions for the pigmentation of linear polyesters, which are prepared by the direct or transesterification process and are preferably further processed into fibers. The aim and task is a uniform pigmentation of the polyester by stabilizing the pigment suspension. According to the invention, this is achieved by adding to the pigment suspension a stabilizer of the formula HO ((CH deep 2) deep m - O) deep n H, where m = 2 n> 1 and n = 1 m> 2. The metered addition of the stabilized suspension takes place to the starting materials or before or during the reprecipitation or esterification action.

Description

Title of the invention

Process for the stabilization of pigment suspensions

Field of application of the invention

The invention relates to a process for the stabilization of pigment suspensions for the pigmentation of linear polyesters, which are produced by the direct or transesterification process and are preferably further processed into filaments.

Characteristic of the known technical solutions

It is known to use for dulling of linear, fiber-forming polyesters of aromatic dicarboxylic acids and linear diols, titanium dioxide having a particle size up to ΪΜ in concentrations of 0.1 to 1.5 wt. % . The addition of the matting agent to the base polymer is generally accomplished in the following ways:

1. Preparation of a Solid Concentrate from the Base Polymer or Its Precursors and the Matting Agent and Dosage to the Polyester Before Spinning (US Pat. No. 3,862,084, US Pat. No. 3,673,147, DE - OS 2 400 228).

2. Preparation of a suspension of titanium dioxide and the linear diol used as the reaction component and addition of this suspension before or during the polycondensation phase (DE-OS 2,601,012, H. Ludewig "Polyester Fibers Chemistry and Technology", Akademie-Verlag Berlin, 1975).

For procedural and energetic reasons, suspension matting is to be preferred. A disadvantage

ri. OtVi. 19R9 * O: -Mi -'i ι r.

However, this process consists of agglomerating the pigment particles suspended in the glycol already in the slurry and dosing into the hot polymer melt. This results in the spinnerets to clog the filter screens and a significant increase in pressure, so that the nozzles leaking fourden and the spinning process must be interrupted. This results in loss of quality and productivity sverrungen.

It is also known to add stabilizers to pigment suspensions which, on the one hand, facilitate the distribution of the pigment in the diol and keep the suspension stable over a longer period of time and, on the other hand, should largely prevent the agglomeration of the pigment in the polymer melt. CH-PS 425 230 describes such stabilizers which are inorganic or organic in nature. As inorganic compounds '' phosphoric acid, boric acid, polyphosphates, sodium silicate, alumina, silica or POlyphosphatsole called. Although these substances, by occupying the impurities in the crystal lattice of the pigments lead to the reloading of the particles and thus delay the agglomeration due to the repulsive forces occurring, but have the disadvantage that they interfere by blocking the polycondensation catalyst or initiation of side reactions in the normal reaction sequence.

As further stabilizers surface-active organic compounds with ionogenic or nonionogenic character are known. These include alkyl phosphates, alkyl sulfonates, alkyl sulfates, oxyethylated fatty acids and Pettalkohole and condensation products of formaldehyde and sulfonated aromatic compounds. Most of these stabilizers have the disadvantage that their thermal stability is insufficient and they are damaged in the subsequent processing stages. In addition, you affect. ·. '''''''' - ..: '-; ^'-'::. · - 3 .-.

surface-active behavior the normal reaction sequence and has an adverse effect on the spinning properties of the polymer melt. , ·

Object of the invention

The aim of the invention is to achieve a uniform pigmentation of linear, fiber-forming polyesters without changing the usual process conditions.

Explanation of the essence of the invention

The invention has for its object to stabilize the pigment suspension used so that the agglomeration of the pigment particles is reduced both in the suspension and in the molten polymer melt and the usual polymer production process is not adversely affected. According to the invention, this is achieved in such a way that the pigment suspension is a stabilizer of the formula

XlU f Vt »W <-J_ - V +" Xl

is added, wherein

at m = 2 η> 1 and at η = 1 m> 2.

Surprisingly, it has been found that compounds of this type, which are chemically very similar to the diol-ethylene glycol most commonly used for the preparation of linear polyesters, stabilize the pigment suspensions. Conveniently, the pigment is stirred into glycol and added to this suspension of the stabilizer. The concentration of the stabilizer is from 0.01 to 10% by weight, preferably from 0.05 to 0.5% by weight, based on the pigment. The concentration of the pigment in the suspension should usually not exceed 25% by weight. The stabilized pigment suspension may already be added to the starting materials, but it should preferably before

or added during the transesterification or esterification reaction. When the stabilized pigment suspension enters the polymerization process, the stabilizers are either chemically incorporated into the base polymer or are evaporated in the subsequent stages at high temperatures and low pressure. The physical and chemical behavior of the stabilizer, which is largely indifferent to the starting materials or the prepolymer, ensures that the usual polycondensation conditions and the technological conditions in the subsequent processes are maintained.

iusführungsbeispiele

Example 1 (comparative example)

204 g of ethylene glycol oil and 36 g of titanium dioxide (TiO ₂ ) as a pigment were used on a laboratory scale with a stirrer at temperatures up to max. 30 ⁰ C for 60 minutes thoroughly mixed. The stability of this suspension decreased by 18.5 % over 48 hours. in the

investigated particle size range 3.8 / * tm - 9.6 / ijm, the proportion of Ti02 ~ agglomerates ^, 5a <h, as measured by particle size analyzer LABORSCALE the company MEDICOR (VR Hungary), 53.4%.

Uach dosage of this suspension in the produced esterification product in an autoclave at a temperature of 280 'C ⁰ and a pressure of 0.1 MPa and subsequent xolykondensation to an average degree of polycondensation P of 110 of Agglomerateanteil was> 5 -Am in the Schmelze.am Heating Table Microscope BOETIUS from VEB Analytik Dresden with 0.7 particles / field of view.

Example 2

It was prepared as in Example 1 but with the addition of 36 mg of dietanediol 1.4 (0.1% by weight , based on the pigment content).

ί - 5. -

proceed to the initial suspension.

The stability of the suspension was still 9-9.5 '# after 48 hours. The Ti0 ₂ agglomerate fraction:> 5 / Hm could be reduced by more than half at 14 % . The agglomerate content in the melt was 0.35 particles / field of view.

Example 3

The procedure was as in Example 1, but with the addition of 36 mg iolyäthylenglykol (molecular weight 600, 0.1 wt.%, Based on the pigment content) to the starting materials for the preparation of the suspension.

Stability was still 99 % after 48 hours . The TiO ₂ agglomerate share> 5 / wn. was 20 % in the specified range . The matting agent in the melt was well distributed and the agglomerate fraction y 5 yiini was 0.4 particles / field of view.

Example 4 (Comparative Example)

Ealne 15% ± ge TiO ₂ suspension was continuously metered into a depressurized working esterification reactor without addition of stabilizer during the esterification reaction at 290 ⁰ G, as (3, a TiO ₂ - concentration in the polymer melt of 0.3% was then effected. Condensation of the product at 280 - 290 ⁰ C and pressures of 20 - 0.25 KPa until an intrinsic viscosity *

+ ei.

0.65 - 0.01 was reached. The product was continuously processed using the classic melt spinning process. The TiO ₂ agglomerate fraction ^ 5 / * / m in the polymer melt was 0.7-0.8 particles / field of view.

Example 5

The suspension was stabilized with 0.1% by weight of 1,4-butanediol 1.4, based on the pigment content, and the procedure was continued as in Example 4. The TiO _p agglomerate fraction

y 5 / ττα in the melt was 0.4-0.5 particles / field of view, r

It has been found that as the TiOp agglomerate fraction in the polymer melt decreases, the number of capillary cracks in the spinning process decreases. Furthermore, there is a direct correlation between agglomerate size and number of deposited TiC> 2 - amount on the filter of the spinneret. A finely dispersed and stable matting agent distribution thus results in an increase in nozzle service life. The number of capillary cracks and nozzle changes in the spinning mill could be reduced by 5 and 30 % respectively compared to Example 4. Overall, a uniform fine matting agent distribution in the single capillary of the Kabe!

Claims (3)

firfindungsanapruch 1. A process for the stabilization of pigment suspensions in the production of linear, fiber-forming polyester by transesterification or direct esterification and subsequent polycondensation, characterized in that the pigment suspension 0.01 to 10 wt.%, Based on the pigment content of the suspension, a stabilizer of the IOrmel HO be added at m = 2 η> 1 and at η «1 m> 2 and the metered addition of this stabilized suspension to the starting materials or before or during the transesterification or esterification reaction. 2 _T method according to item 1, characterized in that the "concentration of the stabilizer is preferably 0.05 to 0.5 wt.%, Based on the pigment content. 3. The method according to item 1 and 2, characterized in that is preferably used as a stabilizer 1,4-butanediol. 4. The method according to item 1 to 3 »characterized in that the stabilizer is preferably added after the combination of the diol with the pigment.