Biaxial forming process for thick-walled acrylic sheet
The present invention relates to a novel biaxial forming process for a preform made of a polymer material which comprises polymethyl methacrylate, to an apparatus for carrying out the process, and also to novel components obtained from a biaxial forming process and their use.
1. A process for producing a biaxially curved component, the process comprising:
a) producing a preform of thickness from 30 to 400 mm from a polymer material, wherein an area A in a central plane of the preform is equal to an area Av in a central plane of the component with a variance of ±40%,
b) introducing the preform into an apparatus so that the preform is freely moveable at edges of the apparatus during the process, and optionally the preform is placed on a female mould,
c) heating the preform to a temperature of from 120 to 170° C., and
d) using a male mould to carry out a forming process on the preform, thereby obtaining the component.
2. The process according to claim 1 , wherein a gap between the male mould at the widest dimension and the female mould is from 0.7 to 1.5 times of the thickness of the preform.
3. The process according to claim 1 , wherein at least one following condition is satisfied:
the preform is moved from below against a fixedly mounted male mould, or the male mould is forced from above into the preform,
the female mould comprises an open or a closed countermould,
an aid to the process is used, optionally a lubricant is applied to at least one of the female mould and the male mould,
an apparatus with reduced-pressure equipment is used,
an apparatus is used in which shaping parts have been designed moveably so that position of the shaping parts are alterable during the process,
an aid apparatus is used by which the preform is forced during the process against the male mould or into a gap formed by the female mould,
and
an apparatus is used in which individual sections of a divided female mould are movable with respect to one another so that gap formed by the female mould is adapted appropriately for ideal shaping.
4. The process according to claim 1 , wherein at least one following condition is satisfied:
a temperature of the preform in the central plane is held constant during the entire process with a variance of up to ±5%,
a preheated preform is introduced into the apparatus,
the entire process takes place in an apparatus with a temperature-controllable housing, a temperature-controllable tooling, or both, where temperatures of the moulds and contact surfaces are controlled to be either identical or different,
and
after the process, the component remains in the mould and is cooled with the mould.
5. The process according to claim 1 , wherein the process is carried out without a holding phase,
or
the process is carried out with one or more holding phases.
6. The process according to claim 1 , wherein the component is subjected to at least one of an internal and an external mechanical finishing process.
7. The process according to claim 1 , wherein at least one following condition is satisfied:
the preform is a preform composed of a single-layer slab or a plurality of layers bonded to one another,
a ratio of a thickness of the preform at the thinnest point to a thickness of the component at the thinnest point is of from 1.0 to 2.0,
the thickness of the preform is from 30 to 300 mm,
and
one or more sacrificial sheets are placed on, under, or both on and under the preform and are subjected together with the preform to the process.
8. The process according to claim 1 , wherein the polymer material comprises polymethyl methacrylate.
9. The process according to claim 8 , wherein at least one following condition is satisfied:
the preform is moved from below against a fixedly mounted male mould, or the male mould is forced from above into the preform,
the female mould comprises an open or a closed countermould,
an aid to the process is used, optionally a lubricant is applied to at least one of the female mould and the male mould,
an apparatus with reduced-pressure equipment is used,
an apparatus is used in which shaping parts have been designed moveably so that position of the shaping parts are alterable during the process,
an aid apparatus is used by which the preform is forced during the process against the male mould or into a gap formed by the female mould,
and
an apparatus is used in which individual sections of a divided female mould are movable with respect to one another so that gap formed by the female mould is adapted appropriately for ideal shaping.
10. The process according to claim 8 , wherein at least one following condition is satisfied:
a temperature of the preform in the central plane is held constant during the entire process with a variance of up to ±5%,
a preheated preform is introduced into the apparatus,
the entire process takes place in an apparatus with a temperature-controllable housing, a temperature-controllable tooling, or both, where temperatures of the moulds and contact surfaces are controlled to be either identical or different,
and
after the process, the component remains in the mould and is cooled with the mould.
11. The process according to claim 8 , wherein the component is subjected to at least one of an internal and an external mechanical finishing process.
12. The process according to claim 8 , wherein at least one following condition is satisfied:
the preform is a preform composed of a single-layer slab or a plurality of layers bonded to one another,
a ratio of a thickness of the preform at the thinnest point to a thickness of the component at the thinnest point is of from 1.0 to 2.0,
the thickness of the preform is from 30 to 300 mm,
and
one or more sacrificial sheets are placed on, under, or both on and under the preform and are subjected together with the preform to the process.