DD288162A5 - PROCESS FOR PREPARING A SIO-LOW 2-DOTED POLYESTER - Google Patents

Abstract

The invention relates to a method for producing a SiO 2 -doped polyester. On the basis of polyethylene terephthalate doped polyester are produced, which are processed into film and stretched biaxially, have specific surface roughness structures and a very favorable sliding, winding and Abrasionsverhalten and are particularly suitable for video players, floppies and high-grade computer buffers. According to the invention, silicon dioxide and titanium dioxide and / or kaolin of particle sizes D50 of maximum 2.0 mm are finely ground together with ethylene glycol with the addition of alkali and an alkaline polyphosphate, subsequently diluted, classified and cationic dispersing assistant added, homogenized and filtered and the suspension mixed with a mixture of dimethyl terephthalate and ethylene glycol added at the beginning of the transesterification. {Polyester; doping; silica; titanium dioxide; Kaolin; Ethylene glycol; Suspension; dimethyl terephthalate; Marriage; classification; filtration; dispersing aids; transesterification; Foil; surface roughness}

Description

Field of application of the invention

The invention relates to a process for producing einos doped polyester, which is due to its nature and special properties after appropriate biaxial stretching to foil documents, in particular for the production of video tapes, floppy discs and high-grade computer tapes, is suitable.

Characteristic of the known state of the art

For the production of magnetic recording materials of high storage densities, polyester materials are used, to which inorganic and / or organic fillers in specific proportions with specific particle size distribution characteristics are added in order to produce specific surface roughness structures and a favorable sliding and abrasion behavior of the carrier film.

Various solutions are described in the patent literature in EP-PS 0199244, FR-PS 2549076, FR-PS 2548858, FR-PS 2561982, DE-PS 2807147, EP-PS 0124291, EP-PS 0132951 and EP-PS 0261430 Fillers preferred particles of silica, titanium dioxide, calcium carbonate, barium sulfate or aluminum silicates used. In almost all of these solutions, the particles of a filler component in the form of ethylene glycol slurries are added to the polyester formation process from the completion of the transesterification reaction. However, this Zufußzuitpunkt allows for many filler inserts optimal Verteilungszustäride the originally very finely divided filler particles in the polyester matrix.

According to known methods, titanium dioxide particles as well as particles of calcium carbonate or barium sulfate are only insufficiently embedded in the polyester matrix and, compared with kaolin or silicon dioxide, lead to greater abrasion of the films produced from such a doped polyester.

It is also known to produce filled polyester, in which several filler components are embedded simultaneously.

Such a polyester is first doped with the required individual filler in the form of a particle suspension and then prepared by mixing with similarly prepared polyesters based on another filler and subsequent extrusion (FR-PS 2561982, EP-PS 0132951).

EP-PS 0261430 describes the use of a combination of spherical silica with calcium terephthalate or kaolin or spherical silica and titanium dioxide or kaolin in the form of ethylene glycol suspensions for doping and minimum average particle sizes for spherical silica of 0.5-0.6 μm for avoidance used unwanted agglomeration. However, only average folio surface roughness values of at least 0.012 μm are achieved while maintaining low abrasion and good lubricity.

Object of the invention

The object of the invention is to develop an effective process for the preparation of a doped polyester derived from ethylene terephthalate as a main monomer building block which, by virtue of its nature and particular properties, can be used for the production of video tapes, floppy disks and high-grade computer tapes. With the incorporation of inorganic filler particles or Teiliihenkombinationen in the polymer matrix in accordance with biaxially stretched films a good sliding and abrasion behavior and at the same time obtaining the average surface roughness Ra less than 0.012 mm is to be ensured.

In order to obtain the mentioned film parameters, it is necessary to produce very stable particle suspensions which have a defined particle size distribution and particle size in order to meet the highest requirements for uniform embedding of the particles in the polymer matrix.

Explanation of the essence of the invention

The invention has for its object to produce a doped polyester based on polyethylene terephthalate, in which the polyester in the course of its production process of dimethyl terephthalate and ethylene glycol, suitable fillers or filler combinations finely divided in an ethylene glycol suspension, to achieve a very good sliding properties of low abrasion and low average surface roughness (Ra = 0.005-0.012 μm) of the films drawn therefrom, at the best time of the polyester-forming process. In this case, fillers are used in average starting particle sizes of not more than 0.2 μm, using intensive milling, which leads to the partial coating of the particles with one another, and also suitable dispersing agents having a dispersing influence in the process of preparing the particle suspension, and especially during the polyester-forming process become.

According to the invention the object is achieved in that a dopant combination of silica and titanium dioxide and / or kaolin, each used in a ratio of 10-90 wt% in%, in the form of an ethylene glycol suspension of 5-15 mass fraction of fillers in%, obtained by joint grinding of particle sizes D ₅₀ rrwimal 2.0Mm in ethylene glycol with the addition of 0.01-0.30 mass% of alkali in% and 0.05-0.50 mass fraction of alkali or alkaline earth polyphosphate in%, followed by dilution and particle classification and addition of 0.01 -0.3 parts by weight in% of a cationic dispersing aid, in each case based on filler, homogenization and filtration, the mixture of dimethyl terephthalate and ethylene glycol in a mass fraction of 0.05-1.0% filler, based on dimethyl terephthalate, at the beginning of the reaction to Achieving an intrinsic viscosity of 0.2 dl / g, zMgeben.

As doping agent, silica having an average particle size of 0.01-0.05 μm in 10-90% by weight in%, preferably 20-80% by weight in% in combination with titanium dioxide and / or kaolin, in 10-90% by weight in%, preferably 20% by weight. 80% by weight, used and milled, with titanium dioxide having an average particle size

of C, 1-0.35pm and kaolin having an average particle size of 0.3-2.0pm, preferably 0.3-0.8mm

Silica is preferably in the form of an ethylene glycol suspension, with alkali or ammonia to a pH of

9-10 set, used.

The dopant combination is preferably combined with pure ethylene glycol over a high-speed Agitator ball mill with high ball filling degree and inserted Glasmahlperlen of 0.8-1.0mm diameter and a Throughput of 80-100 l / h, in 3-4 grinding operations at a suspension temperature of 303-315 K to a suspension of 20 to

40% by mass of fillers homogenized in%.

Before or during the milling, 0.01-0.30 parts by weight of sodium hydroxide solution or potassium hydroxide solution in% and 0.05-0.50 mass fraction Sodium hexametaphosphate or potassium tripolyphosphate added in% and the ethylene glycolic suspension to a

pH adjusted from 8-9.

The combined particle suspension is then loaded for subsequent classification, filtration and process dosing

required working concentration of 5-15 parts by weight of fillers diluted in% with ethylene glycol. Then done

by means of a decanter or separator operating at a throughput of 100-150 l / h or an overflow centrifuge

Separation of particles larger than 1 pm. In ethylene glycol presented cationic dispersant polyethyleneimine, which not only to stabilize the

but also used to obtain a more even distribution of the particles upon incorporation into the polymer matrix, after classification in a concentration of 0.01-0.30 mass% in terms of filler is added to the particle suspension.

The homogenization then takes place via a toothed disc colloid mill and immediately before addition to the mixture Dimethyl terephthalate and ethylene glycol become the particulate suspension of filtration via pirn-shaped yarn package cartridges

1 pm subjected. The combined particle suspension thus prepared is already used in the polyester-forming process of

Time of onset of transesterification to reach an intrinsic viscosity of 0.2 dl / g, but preferably at the beginning of Transesterification at an internal reactor temperature of 370-395 K, metered. The addition of the particle suspension to the mixture of dimethyl terephthalate and ethylene glycol is carried out in a mass fraction

from 0.05-1.0% of filler based on dimethyl terephthalate.

According to the invention, polyesters can be produced, from which biaxially stretched film underlays can be used during further processing

average surface roughnesses of 0.005 to 0.010 pm are achieved, which have a very good Gleitvermägen and little abrasion.

From the polyester doped according to the invention, film is cast which forms a film base for video tapes of thickness 15 μm

biaxially stretched.

Furthermore, this film is biaxially stretched to carrier film for floppy disjs of strength 75μπι. The invention will be explained in more detail below with reference to exemplary embodiments and a comparative example. Embodiment 1

20 kg of silica (50% by weight based on filler mixture) with a mean particle diameter of 0.03 pm and 20 kg of titanium dioxide (50 wt.% In relation to filler mixture) having a mean particle diameter of 0.2 .mu.m are used as filler together with 110 k ( _o pure ethylene glycol with the addition of 50 g potassium hydroxide solution (0.125% by weight based on filler) and 80 g Kalciumtripolyphosphat (0.2 mass% in% based on filler) predispersed in a Zahnscheibenkolloidmühle and then in three Mahlgängen a high-speed stirred ball mill (NAGEMA-HF 20), which with Glass balls of fraction size 0.8-1.0 mm is filled to 90%, charged at 100 l / h throughput The suspension has a pH of 8.5 and is maintained at a temperature of 305K.

This suspension with 26.7% by weight in% filler is then added to 10 parts by weight in% with ethylene glycol to the previously 32 g (0.08% by weight based on filler) of polyethyleneimine, diluted for 2 h via a Zahnscheibenkolloidmühle circulated and then classified an overflow centrifuge. For doping, this suspension in an amount of 0.3 mass% filler in% (based on dimethyl terephthalate) at the beginning of the transesterification reaction of 1480kg dimethyl terephthalate and 1000kg ethylene glycol, when the internal temperature is 373-375K, dosed into the Umasterungsreaktorktor. Immediately before this, a safety filtration of the suspension takes place via yarn winding cartridges made of polypropylene with a pore width of 1 μm.

The film made of this polyester has a very good average surface roughness Ra of 0.008pm. The sliding and abrasion values are sufficient

Embodiment 2

28kg of amorphous silica (70 wt% in% based on filler mixture) having a mean particle diameter of 0.03 (and 12 kg (30 wt% in terms of filler mixture) of kaolin having a mean particle diameter of 0.30pm are incorporated as a filler together with 110kg of pure ethylene glycol the same conditions as in the

Embodiment 1 described, processed into a combined suspension. The pH of the suspension after grinding is 8.7. The diluted, classified, homogenized and filtered Suspension is in 0.3 mass fraction of fillers in% (based on dimethyl terephthalate) at the beginning of the transesterification reaction of

1480 kg of dimethyl terephthalate and 1000 kg of ethylene glycol, at an internal temperature of the transesterification between 373 and 383K metered.

The suspension used has an average particle diameter of 0.10 pm, measured by a on the principle

centrifugal sedimentation automatic particle analyzer CAPA 700 from HORIBA.

The produced from this polyester and biaxially stretched film has a very favorable average Surface roughness Ra of 0.008pm (measured with the perthometer S 6 P) as well as a good sliding and a high Abrasion resistance on.

Vergleichsbeisp'el

In compliance with the operations described in Embodiment 1, silica, titania or kaolin

individually used as a dopant.

Variant 1 Variant 2 Variant 3

Silica titanium dioxide kaolin

Dopant:

Amount 40kg 40kg 40kg

Starting particle size D ₆₀ 0.03 μηι 0.20 μω 0.30 (im

Particle size of the grinding suspension

D ₆₀ 0.03 pm 0.15 pm 0.16 pm

Polyester production:

Metered amount of filler, based

on dimethyl terephthalate 0.4% by weight in% 0.4% by weight in% 0.3% by weight in%

Properties of the stretched film: surface roughness Ra average 0.008 μσι

Sliding behavior and winding capacity insufficient '. Abrasion behavior good

0.009 pm 0.012 pm sufficient Well insufficient Well

Claims (12)

A process for producing a SiO ₂ -doped polyester for video tapes, floppy disks and high-grade computer tapes based on polyethylene terephthalate by mixing a mixture of dimethyl terephthalate and ethylene glycol during the polyester forming process with inorganic filler such as silica, titania, kaolin milled with ethylene glycol, diluted to a concentration of 5-15% by weight in%, filtered and graded, added and the resulting doped polyester is sheeted and biaxially stretched, characterized in that a dopant combination of silica and titania and / or kaolin, used in each case in a ratio of 10-90% by weight, in the form of an ethylene glycolic suspension of 5-15% by weight of filler in%, obtained by joint grinding of particle sizes D ₆₀ maximum 2.0μπΊ in ethylene glycol with the addition of 0.01-0, 30% by weight of alkali in% and 0.05-0.50% by weight proportion of alkali metal or alkaline earth polyphosphate in%, subsequent dilution and particle size classification and addition of 0.01-0.3% by weight of a cationic dispersing aid, in each case based on filler, homogenization and filtration, the mixture of dimethyl terephthalate and ethylene glycol in a mass fraction of 0, 05-1.0% of fillers, based on dimethyl terephthalate, is added at the beginning of the transesterification until an intrinsic viscosity of 0.2 dl / g is reached. 2. The method according to claim 1, characterized in that 20-80 parts by weight of titanium dioxide in% with an average particle size of 0.1-0.3 μητι in combination with 20-80 parts by weight of silica in% with an average particle size of 0.01- 0.05 pm are used and ground. A process according to claim 1, characterized in that 20-80% by weight of kaolin in% having an average particle size of 0.3-0.8 μm in combination with 20-80% by weight of silica in% having an average particle size of 0.01-0 , 05 μιτι be used and milled. 4. The method according to claim 1 to 3, characterized in that before or during the milling 0.01-0.30 part by weight in% sodium hydroxide solution or potassium hydroxide solution and 0.05-0.50 mass in% sodium hexametaphosphate or potassium tripolyphosphate are fed, and a pH is adjusted from 8-9. 5. The method according to claim 1 to 4, characterized in that the combined particle suspension is ground in 3-4 grinding cycles on a high-speed stirred ball mill at a flow rate of 80-100l / h. 6. The method according to claim 1 to 5, characterized in that after dilution, the particle classification by means of a working with a throughput of 100-1501 / h decanter or separator or an overflow centrifuge for particles greater than 1 μηη is made. 7. The method according to claim 1 to 6, characterized in that the particle suspension after classification as a cationic Disper ierhilfsrnittel polyethyleneimine in a concentration of 0.01-0.3 parts by weight in%, based on fillers, is added. 8. The method according to claim 1 to 7, characterized in that the particle suspension is subjected to filtration directly before addition to the mixture of dimethyl phthalate and ethylene glycol. 9. The method according to claim 1 to 8, characterized in that the particle suspension is added to the polyester formation process to start the transesterification at an internal reactor temperature of 370-395 K. 10. The method according to claim 1-9, characterized in that the doped polyester , cast film to a film backing for videotapes of thickness 15 μητι biaxially is stretched. 11. The method according to claim 1 to 9, characterized in that the cast of the doped polyester film is biaxially stretched to a carrier film for floppy disks of strength 75 μηη. 12. The method according to claim 1 to 9, characterized in that the cast of the doped polyester film is biaxially stretched to a carrier film for high-grade computer tapes of thickness 25 μηη.