Container assembly comprising a container and a closure, wherein the container is made of a crystallisable polymer material and comprises a neck portion with an outer cap surface and defines an outlet opening, the neck portion being configured for receiving the closure, wherein the closure includes a closure cap made of a crystallisable polymer material and has an inner cap surface, the closure cap being matched to the neck portion of the container to cover the outlet opening in a closed state, wherein the inner cap surface of the closure cap contacts the outer cap surface of the neck portion when the container assembly is closed, and wherein the material of the inner cap surface of the closure cap and/or of the outer cap surface of the neck portion is crystallised, to allow the container assembly to be opened after being closed for an elongated period of time.

Provided is a new and better solution to the problems associated with the premature softening of PLA filaments in the additive manufacturing of three dimensional articles. It is based upon the finding that poly (lactic acid) filaments with high crystallinity offer much better resistance to heat-induced softening. The crystalline poly (lactic acid) filament can accordingly be used in the additive manufacturing of three dimensional articles without encountering the problems associated with premature softening, such as poor quality and printer jamming. The crystalline poly (lactic acid) filaments can also be used in additive manufacturing of three dimensional articles without compromising the quality of the ultimate product, reducing printing speed, increasing cost, or leading to increased printer complexity. It more specifically discloses a filament for use in three-dimensional printing which is comprised of crystalized poly (lactic acid), wherein said filament has a diameter which is within the range of 1.65 mm to 1.85 mm.

A process for continuous production of partly crystalline polycondensate pellet material which comprises the step of crystallizing the pellet material in a second treatment space (6a) under fixed bed conditions by supply of energy from the exterior by means of a process gas, wherein the process gas has a temperature (T.sub.Gas), which is higher than the sum of the pellet temperature (T.sub.GR) and the temperature increase (T.sub.KR) which occurs due to heat of crystallization released hi the second treatment space (6a), i.e., (T.sub.Gas>(T.sub.GR+T.sub.KR)). The pellets at the exit from the second treatment space (6a) have an average temperature (T.sub.PH), which is 10 to 90 C. higher than the sum of the temperature of the pellets (T.sub.GR) and the temperature increase (T.sub.KR) which occurs due to heat of crystallization released in the second treatment space (6a), i.e., (T.sub.GR+T.sub.KR+90 C.)T.sub.PH(T.sub.GR+T.sub.KR+10).

This invention involves a new and better solution to the problems associated with the premature softening of PLA filaments in the additive manufacturing of three dimensional articles. It is based upon the finding that poly(lactic acid) filaments with high crystallinity offer much better resistance to heat-induced softening. The crystalline poly(lactic acid) filament of this invention can accordingly be used in the additive manufacturing of three dimensional articles without encountering the problems associated with premature softening, such as poor quality and printer jamming The crystalline poly(lactic acid) filaments of this invention can also be used in additive manufacturing of three dimensional articles without compromising the quality of the ultimate product, reducing printing speed, increasing cost, or leading to increased printer complexity. This invention more specifically discloses a filament for use in three-dimensional printing which is comprised of crystalized poly(lactic acid), wherein said filament has a diameter which is within the range of 1.65 mm to 1.85 mm.