EP2454070A1

EP2454070A1 - Device and method for producing thick-walled plastic molded parts having reduced shrinkage sites by injection molding or embossing

Info

Publication number: EP2454070A1
Application number: EP10724351A
Authority: EP
Inventors: Arne Schmidt; Marc Poth; Christian Eberle; Werner Höss
Original assignee: Evonik Roehm GmbH
Current assignee: Roehm GmbH Darmstadt
Priority date: 2009-07-13
Filing date: 2010-05-25
Publication date: 2012-05-23
Also published as: SG177652A1; DE102009027646A1; MX2012000633A; CA2768052A1; BR112012000957A2; US20120171452A1; RU2012104753A; JP2012532777A; CN102470575A; KR20120038964A; TW201127605A; WO2011006704A1

Abstract

The invention relates to a device and method for producing thick-walled plastic molded parts by injection molding or embossing. The device comprises a mold for injection molding or embossing, having a cavity, and is characterized in that the mold comprises a wall region adjacent to the cavity, and a body removed from the cavity and adjacent to the wall region near the cavity, wherein the body of the mold is designed for a temperature T₁ and the wall region is designed for a temperature T₂ different from the temperature T₁. According to the method, the temperature T₂ of the wall region of the mold near the cavity is brought to and held at a value greater than the Vicat temperature T_v of the plastic molding mass before and/or during the injection process, wherein the temperature T₂ is greater than the temperature T₁ of the mold body, and the temperature T₂ of the wall region near the cavity is brought to a temperature below the Vicat temperature T_v of the plastic molding mass during the solidification of the plastic molding mass. The result is thick-walled molded plastic parts, such as optical lenses and the like, having reduced shrinkage sites.

Description

Device and method for producing thick-walled plastic moldings with reduced sink marks by

Injection molding or stamping

The invention relates to an apparatus and a method for producing thick-walled plastic moldings by injection molding or injection compression molding method, wherein the

resulting plastic moldings compared to

conventional devices and methods via a

reduced number and / or expression on so-called

Have sinks.

In particular, the invention relates to a

Device and a method for the production of

Plastic moldings with wall thicknesses of more than 3 mm, advantageously more than 5 mm, particularly useful more than 8 mm, wherein the plastic moldings from thermoplastic molding compositions, preferably PMMA, obtained by injection molding or injection-molded.

Such thick-walled plastic moldings are

For example, plastic lenses for spectacles. Thermoset castings (CR39) and

thermoplastic molding compounds are used, depending on the purpose of use polystyrene, polymethylmethacrylate ..

Polymethyl methacrylimide, cyclo-olefin copolymers,

Polycarbonate or copolycarbonate can be used.

In known processes, lens blanks of uniform wall thickness are produced in cycle times of less than 30 seconds, and normally a standard injection molding process is used. The molding compound is in the filling phase via small-sized channels in the cavity of the tool brought in. Because amorphous plastics in the cooling phase, a high density reduction in the range up to 10

Volume percent or more will learn this

Material shrinkage in a subsequent post-pressure phase compensated by replenishment of plastic melt safe from the injection piston of the injection molding.

In a standard injection-compression molding process, in contrast to the standard injection molding process, the plastic compound is introduced into a pre-enlarged cavity in a first filling phase, and this plastics molding compound is subsequently embossed by means of an axial tool embossing. The

Mass weight, which is introduced in the first filling phase in the vorvergrößerte cavity, corresponds to the mass weight of the later removed parts. With the axial tool movement becomes the pre-enlarged cavity

reduced and the remaining filling of the cavity is

performed. The standard injection compression molding process is used for simple optical parts to avoid sink marks as a result of material shrinkage.

In addition, however, surface markings can also result because the plastic molding compound can not flow into the cavity in an optimum source flow. It can be cold edge layers in the filling phase

move. By increasing the mold temperature to near the glass transition temperature, the formation of cold

Suppressed surface layers. However, this results in a prolonged cycle time.

In order to ensure an almost optimal source flow, large partial cuts are required, which then have to be cut off dust-free and usually no longer for the production of optical parts can be used.

Nevertheless, in the production of thick-walled plastic moldings, for example optical lenses made of thermoplastic molding compositions, injection molding or injection-compression techniques, such as stamping,

Expansion molding or sequential embossing, the problem of avoiding so-called "sink marks" is a very central thick-walled moldings are usually such moldings, which have at least one point over a wall thickness of at least three millimeters, especially at molding thicknesses of five millimeters, eight Millimeters or thicker can be recognized after cooling and demolding "sunken spots". These are generally those parts of the finished molded body, at which the increased free shrinkage (volume reduction) of the material leads to errors with too small material thickness. Although theoretically this phenomenon can be counteracted by an increase in the screw back pressure, an increased screw back pressure results in an additional stress load of the thermoplastic material and can possibly lead to a

Lead molecular orientation in the molding. Especially at

However, moldings such as lenses for optical applications, this is very disadvantageous, since this deteriorates the optical quality of the molded part.

From DE 199 13 525 A1 = document 1 or D1 is a

Method of shaping plastic moldings with

Compensation of the volume reduction of the material known.

According to the Dl a method is disclosed in which the hardening or cooling-induced volume reduction of pressurized material in the cavity by a reversible dependent on the pressure inside the cavity

Extension of the mold cavity is compensated. This is achieved for example by attaching systems for generating a compression-pressure-dependent counterforce in the form of introduced into the cavity elastic elements. While such an approach may be suitable for reducing shrinkage on a case-by-case basis, it is complex and has not been established in the practice of injection molding or stamping.

Another proposal for producing thick-walled

Moldings can be found in DE 100 48 861 A1 = Document 2 or D2. The D2 describes a method and an apparatus for producing thick-walled blanks for optical lenses, in which one proceeds in two stages. In a first stage, a thin lens is first passed through

Injection molding made in the second

Production stage increased by supplying plastic material to its final thickness, i. "Inflated" is.

Although the surface quality of thick-walled moldings in this way to the quality of thin-walled moldings

will be used to reduce the

Shrinkage and the reduction of the consequent

Sinkholes, after the first phase or the second phase according to D2 an additional compression phase needed. Thus, the problem of molecular orientation continues during the holding phase. From DE 101 14 228 Al = document 3 or D3 is a

A method for equalizing the shrinkage behavior of a molded part both between individual cavities of a multiple tool and from cycle to cycle of a Injection process known. This will be the temperature

and / or an internal pressure in the cavity monitored and by a temperature control of the tool from the end of the filling phase or from a pressure maximum in the cavity to the end of the injection cycle to a reference curve

adjusted.

WO 2004/058476 A3 = document 4 or D4 discloses a method for controlling the production of molded parts.

According to the proposal of D4, the temperature of the

Tool regulated. Furthermore, the cavity and / or the mandrel are directly heated or cooled. The basic idea of the D4 is to regulate the temperature of a cavity or a mold core (= stamping die) not only via the cooling circuit but with the help of heating elements. Becomes

found that cavity or mold core have too low a temperature, the heating elements are regulated higher. Is the temperature in the cavity or at

Mold core too high, the circulation in the cooling circuit is increased. The goal is in any case, printing and

Temperature conditions in the cavity to keep constant.

Nevertheless, the proposed in accordance with the D3 and D4 control of the mold temperature in the injection molding process is in need of improvement. According to D3 and D4, the temperature control seems to be relatively sluggish.

In addition, the complete cavity is always closed too

what next to one temper the cycle times

impairing inertia also increased

energetic effort leads. In view of the prior art mentioned and discussed herein, it was an object of the invention to provide a

Device for producing thick-walled

Plastic moldings by injection molding or

Injection molding process, to provide the easy

is constructed.

Furthermore, the creation of a device has been the object of the invention, which as possible with simple means but still very variable in the production of

Plastic moldings, preferably made of thermoplastic materials, with relatively high optical quality permitted.

Yet another object of the invention was a

Specify device for the production of thick-walled moldings, which allows the shortening of the cycle times during injection molding or injection-compression molding.

Furthermore, the shortened cycle time should not be at the expense of a holding pressure phase or a prolonged holding pressure phase.

Another object of the invention is to provide a method for producing thick-walled plastic moldings by injection molding or injection-compression molding, the method should enable fast, safe and cost-effective the production of plastic bodies, with simple means.

In procedural terms, there was also the

Task, injection molding or injection molding so too

design that the resulting plastic moldings compared to conventional devices and methods over a reduced number and / or expression on so

incidence points These tasks are solved as well as other tasks that are not literally mentioned in detail, but which are readily apparent from the introductory discussion of the prior art or how

Of course, can be derived by a device with all features of claim 1.

Advantageous embodiments of the invention

Device are the subject of the independent

Device claim related claims. In procedural terms, the features of the independent method claim provide a solution of the

Invention with regard to the method aspects

underlying problem. advantageous

Process variants are in those of the independent

Process claim dependent procedural claims under protection.

Finally, the claims of the use category protect the use of the method of the invention.

In particular, characterized in that an apparatus for producing thick-walled plastic moldings by injection molding or stamping, comprising a tool for injection molding or - embossing with a cavity, is characterized in that the tool adjacent to the cavity

Includes wall portion and adjacent to the near-cavity wall region cavity distant body,

wherein the body of the tool to a temperature Ti and the wall area to a temperature different from the temperature T ₂ T ₂ tempered, it is possible to improve the known devices to streamline the production of thick-walled plastic moldings and all of the standards institutes and the industrial workers with respect to the physical and chemical properties of the resulting molded articles outstanding requirements. In particular, the resulting shaped bodies have regard to the number and / or the expression of

Drop marks a significantly reduced level compared with moldings that can be obtained using known devices. It is also

According to the invention possible, a large number of additional

To realize advantages.

These include:

=> Shortened cycle times through optimal

Process temperatures during injection molding or

Injection-compression molding. => Optimal process temperatures in relation to the

Shrinkage conditions in the molded part.

=> For moldings with differences in wall thickness, the beneficial effect of the method

in particular the thicker wall areas of the molding. => Equal pressure distribution or

Embossing pressure distribution and thereby avoidance or

Reduction of sink marks on the molded part.

=> Less or no molecular orientation, which improves the optical quality of, for example, lenses.

=> Excellent dimensional accuracy of the molded parts.

=> Longer and more effective compression phase, as no

Premature frozen edge layers arise.

The device of the invention for producing thick-walled plastic moldings by injection molding or stamping comprises a tool for injection molding or stamping with a

Cavity .

The term "injection molding or injection molding tool" is synonymous with the terms "injection molding tool"

Unless otherwise indicated, the term "tool" is always to be understood cumulatively to mean an injection molding tool and an injection compression molding tool. These terms are well known to those skilled in the art. The tool of the device according to the invention has a cavity. This is understood in the context of the invention, a cavity, the injection molding or

Injection molding process with thermoplastic material

is replenished. It is clear that the invention is not limited to tools with a single cavity.

Similarly, the invention includes devices with tools that have more than one cavity, be it in one or more parting planes.

For the purposes of the invention, a tool is characterized inter alia by the fact that it is attached to the cavity

adjacent wall portion and adjacent to the near-cavity wall region cavity distant body. The tool encloses one or more cavities and, viewed from a cavity, the area of the tool becomes the region of the tool close to the cavity

denotes, which adjoins the cavity and limits this. Furthermore, the one from the direction of the cavity is considered at the cavity near wall region of the cavity

Tool subsequent cavity farere area of the

Tool the so-called body or cavity-distant body of the tool. The thickness or thickness of the near-cavity wall portion of the tool can vary over a wide range. Likewise, the thickness or thickness of the

cavity-distant body of the tool vary over a wide range. In general, the ratio of Thickness of the near-cavity wall area of the tool to the thickness of the cavity-free area of the tool in the range of 1: 100 to 2: 1. Here, the ratio for a tool can be constant. However, it may look different for a tool in several places

Thickness ratios come, depending on the specific structure of the tool and the special process requirements for the tool.

In the context of the invention, it has proven to be advantageous

proven, when the thickness of the near cavity wall portion of the tool equal to or smaller than the thickness of the

cavity-far body of the tool is. It is particularly advantageous if the thickness of the close to the cavity

Wall area designed as low as possible compared to the kavitätsfernen body. So have for that

Ratio of the thickness of the near-cavity wall area to the cavity-distal body of the tool Values in the range of not greater than 1: 2, more suitably not greater than 1: 5 and most suitably not greater than 1:10

especially proven. In particularly preferred

inventive devices is the said

Ratio in the range of 1: 8 to 1: 2, more preferably in the range of 1:10 to 1: 5 and more conveniently in the

Range from 1:20 to 1:10.

Based on the total thickness or thickness of the tool, the thickness of the near-cavity wall portion of the tool may also extend over a wide range.

In a preferred embodiment, the device of the invention is characterized in that the thickness of the

Wall area between about 1/20 to 1/4 of the total thickness of the tool cavity remote body and near cavity wall area makes. Even more preferred for the device is when the thickness of the wall portion is about 1/10 to 1/5 of the total thickness of the cavity far wall and cavity near wall cavity tool. The device according to the invention is characterized in particular in that the body of the tool is at a temperature Ti and the wall area at one of the

Temperature Ti different temperature T _{2 are formed} tempered. This configuration allows

advantageous the different temperature of the

Wall area and the body of the tool in a very short time. The previously observed in practice relatively high inertia of the temperature behavior of the entire tool body can be significantly reduced by a carried out in view of the separate Temperierbarkeit decoupling of the near-cavity wall portions of the tool from the rest of the body of the tool. From this

results in particular advantageous the possibility of setting higher temperatures in the cavity near the cavity of the tool, with the result that the ultimately acting on the introduced into the cavity plastic material heat a higher temperature of the plastic material

causes. Likewise, by the respect

Temperability decoupling of wall area and residual body of the tool the possibility that the near-cavity

Tempered edge regions of the tool for a longer period of time, as is the case with conventional devices, with the result that the number of

Sink marks or the expression, that is the

Intensity of sink marks, is reduced compared to conventional devices.

The cavity near wall area of the tool and the rest of the body can be in terms of

Temperability in different ways from each other decouple. Thus, it may be possible to provide the cavity near areas of the tool with a special coating, which can be controlled for example via resistance heaters or inductively. Here you can

Professional per se known coating materials for

Use come, such as thermo-ceramic coatings. However, the subsequent coating of existing tools can be somewhat costly.

It is therefore preferred in the sense of the invention that the near-cavity wall portion of the tool and the

cavity-distant body of the tool have separate temperature control circuits. In this way, the temperature differences between the wall portion of the tool and the rest of the body of the tool in a quick, easy and convenient way

realize.

The control of the two temperature control can be done in different ways. In addition to the already mentioned control via resistance heaters or an inductive control, it is possible to use the temperature

liquid media, such as water, oil or steam to regulate.

In the context of the invention, it has proven to be particularly advantageous insofar

the near-cavity wall area of the tool is replaceable. An expedient device according to the invention therefore has an exchangeable cavity frame, which is preferably made of steel. This is an inner lining of the mold cavity, the

made interchangeable and the tool body and the cavity separated from each other. The advantages of a

interchangeable cavity frame consist mainly in the fast and individual adaptability of the frame to new Kavitätenformen and the possibility of quick replacement. It is also possible to use the cavity frame to produce from such materials, which have a very low inertia in terms of temperature behavior. The use of such comparatively expensive

Materials then remains at a relative to the entire body relatively low mass or volume fraction

limited.

As already stated, the device of the invention is preferably suitable for injection molding.

Another preferred application of the

Device according to the invention is also the injection-compression molding. In contrast to injection molding, the device in the

Injection molding additionally has a movable mold core or embossing stamp. Here, it is within the scope of the invention of particular interest and preferred that the mandrel or die separately to a temperature T _3rd

is formed tempered. This variant can

be used in particular, via the stamper additional energy in the cavity located in the

Material to bring, with the result that the quality of the resulting molded part can be further increased. In an expedient embodiment, this idea is so

realized that the mandrel or die has a coating of thermo-ceramic.

The invention also provides a method for

Production of thick-walled plastic moldings with reduced in terms of number and / or expression

Drop marks by injection molding or embossing, in which one

a device as provided hereinabove; - Injects a thermoplastic molding compound in the flowable state in the tool of the device; - causes the injected plastic molding compound to solidify; and - the solidified plastic molding demolded; where you are

- The temperature T _{2 of} the near-cavity wall portion of the tool before and / or during the injection process to a value greater than the Vicattemperatur T _v of

Plastic molding compound brings and holds, wherein the temperature T _{2 is} greater than the temperature Ti of the tool body; and

- The temperature T _{2 of} the near-cavity wall area during solidification of the plastic molding material and before demolding to a temperature below the Vicat temperature T _v brings the plastic molding compound.

According to this procedure, it is possible to temper the edge region of the molded part higher and possibly longer, with the result that a reprinting effect or embossing force can be maintained for a longer time. Under Vicat temperature T _v , the Vicat

Softening temperature (VST = Vicat softening temperature) according to DIN EN ISO 306 (precursor: DIN 53460) understood. The Vicat temperature is measured with a needle (with a circular area of 1 mm ² ). This is loaded with a test load of 10 N (test load A) or 50 N (test load B).

The test specimen with a permissible thickness of 3 to 6.4 mm has a defined heating rate of 50 or 120 K / h

exposed. The VST is reached when the indenter reaches a penetration depth of 1 mm. By varying the boundary conditions, four parameter combinations result, namely, VST / A50, VST / A120, VST / B50, and VST / B120, for which purposes the VST / B50 method is used for purposes of the invention unless otherwise specified.

Basically, in the method of the invention of

Cavity near wall area, particularly useful the Kavitätsrahmen described above, the tool before and / or tempered during the injection process by means of suitable heating to a higher temperature level, compared with the temperature level of the rest of the body of the tool. The temperature control of the cavity-near edge region, preferably of the cavity frame, is expedient cyclically to the injection molding or injection-compression cycle. During the injection phase, it is also appropriate, the

Close to the cavity edge area, preferably in the form of

interchangeable cavity frame, on a high

Temperature level above the Vicat temperature of the

injected plastic material to maintain a long reprint or embossing pressure. After uniform solidification of the plastic melt brings the cavity near cavity wall area means

suitable cooling back to a temperature below the Vicattemperatur of the plastic material, namely the

Demolding temperature.

As already stated, there is an advantage of

method according to the invention in that the inertia of the tool with respect to temperature changes

overcomes and thus despite high temperatures on the molded part and despite prolonged Nachdruckwirkung or despite prolonged impact of the embossing force makes fast cycle times feasible. In this context, it is advantageous if the differences between the temperature level T2 of the cavity-near wall area and the temperature level Ti of the rest of the tool body are as large as possible.

Accordingly, a particularly expedient modification of the method according to the invention is characterized in that a Difference Δ _T2 i between the temperature T ₂ of the kavitätsnahen wall portion and the temperature Ti of the kavitätsfernen

Tool body of more than 20 ⁰ C sets.

An even more preferred variant provides that a difference Δ i _T2 between the temperature T ₂ of the kavitätsnahen wall portion and the temperature Ti of the kavitätsfernen

Tool body of more than 40 ⁰ C sets.

Such a temperature difference has a particularly advantageous effect on the reduction of the sink marks of the finished moldings.

In a further favorable modification of the method is provided that the cavity near wall region of the tool by means of liquid media, by means of

Resistance heating or inductively tempered, particularly useful by means of liquid or gaseous media, such as oil, water or steam.

The principle of the invention can be transferred to the known injection molding and injection compression molding processes. However, its particularly advantageous effects come to light in the production of thick-walled molded articles made of plastic.

It is expedient to use the process of the invention for the production of thick-walled injection-molded or injection-molded parts with wall thicknesses of more than 5 mm. A further advantageous use comprises the

Production of thick-walled injection molding or

Injection-molded parts with wall thicknesses of more than 8 mm.

The process of the invention is suitable for the production of molded parts from thermoplastics, such as

Polystyrene, polycarbonate, copolycarbonate, cyclo-olefin

Copolymers, polymethyl methacrylimide or polyacrylates and methacrylates. A particularly appropriate use relates to the production of PMMA moldings, most preferred are lenses for optical purposes.

In the following the invention is based on

Exemplary embodiments and comparative examples below

Reference to the attached figures explained in more detail.

In the figures show:

1 shows a cross section through an idealized and simplified representation of a tool with a

Kavitätsrahmen; FIG. 2 shows a cross section through a partial view of an embodiment of a device according to the invention;

FIG. 3 shows a diagram of the thickness distribution in relation to a cold frame; and

Figure 4 is a diagram of the thickness distribution with respect to a hot frame.

List of reference numerals for FIGS. 1 and 2:

1 cavity frame

2 cavity

3 tool

3a Movable tool side

3b Fixed tool side

4 stamps

5 Tool plate In the figure 1 can be seen a cross-sectional view of a schematic diagram of a tool. Reference numeral 3 denotes a mold for injection molding. The tool 3 has in its interior a cavity 2. The

Cavity 2 is also referred to as cavity 2. Furthermore, it is possible to see a wall area 1 close to the cavity and a wall cavity-distant body 5 of the tool. The edge region 1 is adjacent to the hollow space 2. From the cavity 2 to the outside

considered close to the cavity near wall region 1 of the cavity distant body 5 of the tool 3.

Cavity near wall area 1 and cavity-distant area or cavity-distant body 5 of the tool together form the entire body of the tool 3.

In the figure two can be seen as tool components, the plates 3a and 3b. In this two-platen tool, the cavity 2 is integrated in the plate 3a, while the plate 3b can be opened to demould a finished injection-molded part.

It can be seen very well that the cavity 2 in the assembly 3a is surrounded by a kind of frame 1. This

Cavity frame 1 is designed replaceable in the example shown and separately tempered. Furthermore, one recognizes in FIG. 2, the embossing punch 4, which can be used for compaction of the molding compound in the cavity.

It is understood that the back wall of the cavity, that is the one formed by the assembly 3b of the tool

Limitation of the cavity may also be formed separately tempered. However, this is not necessary to achieve the beneficial effects of the invention.

In Figure 3, the component thickness distribution is shown with respect to the cold frame. In FIG. 4, the

Component thickness distribution in relation to the hot frame shown.

Claims

claims

1. Apparatus for producing thick-walled

Plastic moldings by injection molding or stamping, wherein the resulting plastic moldings in

Having regard to number and / or expression reduced sink marks, comprising a tool for injection molding or stamping with a cavity, characterized in that the tool adjacent to the cavity

Wall region and an adjacent to the cavity near wall region cavity distant body comprises, wherein the body of the tool to a temperature Ti and the wall region are formed to a different temperature T ₂ different temperature T ₂ .

2. Apparatus according to claim 1,

characterized s the s,

the near-cavity wall area of the tool is a replaceable cavity frame made of steel.

3. Apparatus according to claim 1 or 2,

characterized s the s,

the cavity-near wall region of the tool and the cavity-distant body of the tool have separate temperature-control circuits.

4. Device according to one of the preceding claims, characterized gekennzei chnet the s,

the thickness of the wall portion is between about 1/20 to 1/4 of the total thickness of the cavity far body tool and the cavity near the cavity wall.

5. Device according to one of the preceding claims, characterized gekennzei chnet the s,

the thickness of the wall portion is about 1/10 to 1/5 of the total thickness of the cavity-cavity body and cavity-near wall area tool.

6. Device according to one of the preceding claims 1 to 5 for injection molding.

7. Device according to one of the preceding claims 1 to 5 for injection-compression molding.

8. Apparatus according to claim 7

having a movable mandrel or

Die,

characterized in that

the mandrel or die separately on a

Temperature T _{3 is formed} temperable.

9. Process for producing thick-walled

Plastic moldings with reduced in terms of number and / or expression sink marks

Injection molding or embossing, in which one

- Provides a device according to claims 1 to 8; - A thermoplastic molding compound in

flowing state injected into the tool of the device;

- causes the injected plastic molding compound to solidify; and

- The solidified plastic molding demolded; where you are

- The temperature T _{2 of} the near-cavity wall portion of the tool before and / or during the injection process to a value greater than the Vicattemperatur T _v brings the plastic molding composition and holds, the

Temperature T ₂ greater than the temperature Ti of

Tool body is; and - the temperature T _{2 of} the near cavity wall area during the solidification of the plastic molding material and before demolding to a temperature below the

Vicattemperatur T _v brings the plastic molding compound.

10. The method according to claim 9,

characterized gekennzei chnet, the s

to T ₂ of the kavitätsnahen wall portion and the temperature Ti of the kavitätsfernen tool body of more than 20 ⁰ C adjusts a difference _Δ τ2 i between the temperature.

11. The method according to claim 9,

characterized gekennzei chnet, the s

to set a difference Δ _τ2 i between the temperature T _{2 of} the near-cavity wall portion and the temperature Ti of the cavity distant tool body of more than 40 ⁰ C.

12. The method according to any one of claims 9-11,

characterized in that

the cavity-near wall area of the tool is tempered by means of liquid media, by means of resistance heating or inductively.

13. Use of a method according to one of

preceding claims 9 - 12 for the production of thick-walled injection or injection-molded parts with wall thicknesses of more than 5 mm.

14. Use according to claim 13 for the preparation of

thick-walled injection-molded or injection-molded parts with wall thicknesses of more than 8 mm.

15. Use according to claim 13 or 14 for the production of PMMA moldings.

16. Use according to claim 15 for the preparation of

optical lenses.