NL8301456A - POWDER PRINTING MATERIAL BASED ON ALGINATE; METHOD FOR PREPARING THEREOF - Google Patents

Description

* VO 4749

Powdered impression material based on alginate; method for preparing it.

The invention relates to a powdered printing material based on alginate, and to a method for preparing it.

A powdered impression material based on alginate 5 is known from British patent 518,596. It is used in dentistry to make dental impressions. To this end, the powdered impression material is mixed with a measured amount of water shortly before use to obtain a paste with which a denture can be made. Curing occurs after some time. The impression is then used to make a positive model of the denture from plaster.

The existing powdery impression materials contain a soluble alginate, eg the potassium or sodium salt of alginic acid, as well as a compound of a metal which forms an insoluble compound with alginic acid, usually a calcium salt, such as calcium sulfate.

In order to prevent too rapid the formation of insoluble alginate, eg calcium alginate, and thus too fast curing after mixing with water, a compound is also present which forms an insoluble compound with the intended metal, usually a phosphate, such as sodium pyrophosphate. Also, the powdered impression material contains one or more inert fillers to promote a suitable consistency and a good mixing of the active ingredients, e.g. clay, silica, and infusion earth. Finally, various other components such as fluorides, dyes and flavors may be present.

An important drawback of the known alginate impression materials, however, is that they cannot properly reproduce the finest details of the teeth on the positive plaster model, which is attributed to a reaction of unreacted alginate with the plaster, whereby the impression is cast, with the result that the surface of the positive plaster model becomes rough and the tails are lost.

It has now been found that this drawback is overcome by 8301456 i -2- a powdered impression material based on alginate, characterized in that it is a nonionic surfactant consisting of a poly (oxyethylene) poly (oxypropylene) poly (oxyethylene) polymer.

In particular, according to the invention, a liquid non-ionic surfactant of the Pluronic type is used. Pluronic L 61, L 81 and L 101 are suitable, for example, which are not too viscous. Of these, Pluronic L 61 and L 81 both satisfy very well, but because of the somewhat bitter taste of the former type, the use of Pluronic L 81 is most preferred.

In practice, the nonionic surfactant will make up 2-10% by weight of the impression material. The best results are obtained at a content of 3-5% by weight.

It has also been found that the properties of the impression material are further improved by the presence of 5-15 wt% kaolin (promotes rapid water uptake) and 1-3 wt% talc (promotes intermixing).

Incidentally, the non-ionic surfactant used according to the invention also has a positive influence on the rate at which water is absorbed into the impression material (wetting rate), while moreover the tendency of the powdery impression material to be dusted is reduced.

The invention also provides a method for preparing a powdered impression material based on alginate, which is characterized in that the alginate is mixed with a filler and optionally other conventional components and during mixing a non-ionic surfactant, consisting of a poly (oxyethylene) -poly (oxypropylene) -poly (oxyethylene) polymer, is sprayed onto the mixture.

It is preferred that a liquid Pluronic nonionic surfactant be sprayed on the mixture. Most preferably, Pluronic L 81 is sprayed on the mixture. By preheating the non-ionic surfactant, preferably at 20-120 ° C, most preferably 60-80 ° C, the viscosity is reduced and therefore a faster and more homogeneous mixing with the powder mixture. of the other components.

This mixing preferably takes place in a blade mixer, most preferably an Lddige mixer, which is provided with one or more spray nozzles in the wall, whereby the non-ionic surfactant is atomized.

The liquid pressure on the spray nozzles will in practice be chosen between 0.1 and 20 MPa, with a pressure between 3 and 5 MPa being preferred.

According to a particularly preferred embodiment, 10-50 wt% of the filler is pre-ground with kaolin and talc in such amounts that the final impression material contains 5-15 wt% kaolin and 1-3 wt% talc.

The invention is explained in more detail below with reference to an example and some comparative examples.

The plaster compatibility and the detail representation of the alginate impression material was measured according to the method of ISO specification No. 1563.

Example I

20 An alginate impression material was composed as follows:

Potassium alginate 14.0%

Calcium sulfate 10.0%

Magnesium oxide 2.0%

Potassium titanium fluoride 2.5% 25 Sodium pyrophosphate 1.0%

Titanium dioxide 5.0%

Dye 0.1%

Flavor 0.1%

Infusion head 52.3% 30 Kaolin 7.5%

Talk 1.5%

Pluronic L 81 4.0%

The kaolin and talc were ground in a ball mill with 20% of the required amount of infusion earth for 2 hours.

This mixture was then placed in a Lödige mixer together with the other raw materials, except Pluronic.

8301456 w l -4-

The required amount of Pluronic was heated to 70 ° C in a vessel with an electric heating element. Using a pump, the liquid was forced through four spray nozzles mounted in the wall of the Lödige mixer. The liquid pressure was 4.5 MPa. The Lödige mixer was in operation during the misting process.

The result was an alginate impression material, which was readily miscible with water, gave no dust formation and had very good plaster compatibility and detail reproduction.

A plaster model, made with this impression material according to the detail display test of ISO 1563, had a very smooth surface and produced the finest line, namely the 20 µm line.

Comparative example 1

The same alginate impression material as in Example I 15 was formulated, with Pluronic omitted. The grinding and mixing procedure was kept the same.

With the impression material obtained in this way, it was not possible to reproduce a 20 µm line with the detail display test, while the plaster surface was considerably less smooth than 20 of the model obtained in Example I.

Comparative example 2

The same alginate impression material as in Example I was formulated, with Pluronic omitted.

The raw materials were mixed directly, without grinding, in a Lódi-25 mixer. With the impression material obtained in this way, it was not possible to reproduce 20 µm with the detail display test, while the plaster surface was considerably less smooth than that of the model obtained in Example I. The resulting powder was more difficult to mix to a homogeneous paste with water than the powders of Example I and Comparative Example 1.

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Claims (15)

Powdered impression material based on alginate, characterized in that it comprises a non-ionic surfactant consisting of poly (oxyethylene) polypropylene propylene (oxyethylene) polymer. Printing material according to claim 1, characterized in that it comprises a liquid non-ionic surfactant of the Pluronic type. Printing material according to claim 2, 10, characterized in that it comprises Pluronic L 81. Printing material according to one or more of claims 1 to 3, characterized in that it contains 2 to 10% by weight of the nonionic surfactant. Printing material according to claim 4, characterized in that it contains 3-5% by weight of the non-ionic surfactant. Printing material according to one or more of claims 20 to 1, characterized in that it contains 5-15 wt.% Kaolin and 1-3 wt.% Talc. 7. Process for preparing a powdered impression material based on alginate, characterized in that the alginate is mixed with a filler and optionally other usual components and during mixing a non-ionic surfactant consisting of a poly (oxyethylene) poly (oxypropylene) poly (oxyethylene) polymer, the mixture is sprayed. Process according to claim 7, characterized in that a liquid non-ionic surfactant of the Pluronic type is sprayed on the mixture. 8301456 0 *, -6- V Process according to claim 8, characterized in that Pluronic L 81 is sprayed on the mixture. Method according to one or more of claims 7-9, 5, characterized in that the non-ionic surfactant is preheated. 11. Process according to claim 10, characterized in that the non-ionic surfactant is preheated at a temperature between 20 and 120 ° C, most preferably 60-80 ° C. Method according to one or more of claims 7-11, characterized in that the non-ionic surfactant is sprayed under a pressure of 0.1 to 20 MPa, preferably 3 to 5 MPa. Method according to one or more of claims 7-12, characterized in that 10-50% by weight of the filler is pre-ground with kaolin and talc in quantities such that the final impression material is 5-15% by weight kaolin and contains 1-3 wt% talc. Method according to one or more of claims 7-13, characterized in that the mixing takes place in a blade mixer. 15. Method according to claim 14, characterized in that a Lódige mixer is used with one or more spray nozzles in the wall, whereby the non-ionic surfactant is atomized. &&&&& 8301456