Disclosed are biaxially stretched polyolefin films containing 10 to 45% by weight of a cycloolefin polymer with a glass transition temperature between 12 and 170 C., and 90 to 55% by weight of a semi-crystalline alpha-olefin polymer with a crystallite melting temperature between 15 and 170 C. The glass transition temperature of the cycloolefin polymer is less than or equal to the crystallite melting temperature of the alpha-olefin polymer, and the polyolefin film has a shrinkage at 130 C. after 5 minutes, as measured according to ISO 11501, of less than or equal to 2%. These polyolefin films are excellently suited as dielectrics for capacitors and are distinguished by a low shrinkage at high temperatures. The cycloolefin polymer preferably forms a co-continuous phase in a matrix of the semi-crystalline alpha-olefin polymer, providing improved mechanical and electrical properties including a dielectric strength from 500 to 750 V/m.

A film material formed of thermoplastic polymer material is processed so as to have linearly extending regions (A) linked together by linearly extending webs (B), regions (A) and webs (B) each being oriented, the dominant direction of orientation in regions (A) forming an angle (V) to the direction on which (A) extends and webs (B) comprising arrays of linear furrows of thinner material or splits forming angles (U) higher than (V) to the direction in which (A) extends. The method of producing the new film involves passing an orientated film through a pair of intermeshing grooved rollers to cold-stretch the film in a direction at an angle to the predominant original orientation, at least one of the grooved rollers having crests with sharp edges to form the division between regions A and webs B and to stretch the material to form webs B while stretching the material less or not at all to form regions A. Preferably at least one of the grooved rollers has crests with a waved surface shape.

In the pultrusion of reinforced plastic profiles in strand form, the strands of the reinforcement are brought together in a positioning device and subsequently embedded in the plastic. The pulling of the strands of the reinforcement through the positioning device leads to an unwanted contraction and uncontrolled positioning of the reinforcement in the plastic profile. The invention envisages forming the positioning device by multiple successive positioning means, of which at least some positioning means can be periodically moved forward in the direction of production and also moved back counter to the direction of production. As a result, there is an alternating tensioning and compression of individual regions of the reinforcement. This makes exact positioning of the reinforcement in the plastic profile possible and prevents contraction of the reinforcement.

In the pultrusion of reinforced plastic profiles in strand form, the strands of the reinforcement are brought together in a positioning device and subsequently embedded in the plastic. The pulling of the strands of the reinforcement through the positioning device leads to an unwanted contraction and uncontrolled positioning of the reinforcement in the plastic profile. The invention envisages forming the positioning device by multiple successive positioning means, of which at least some positioning means can be periodically moved forward in the direction of production and also moved back counter to the direction of production. As a result, there is an alternating tensioning and compression of individual regions of the reinforcement. This makes exact positioning of the reinforcement in the plastic profile possible and prevents contraction of the reinforcement.

A film material formed of thermoplastic polymer material is processed so as to have linearly extending regions (A) linked together by linearly extending webs (B), regions (A) and webs (B) each being oriented, the dominant direction of orientation in regions (A) forming an angle (V) to the direction on which (A) extends and webs (B) comprising arrays of linear furrows of thinner material or splits forming angles (U) higher than (V) to the direction in which (A) extends. The method of producing the new film involves passing an orientated film through a pair of intermeshing grooved rollers to cold-stretch the film in a direction at an angle to the predominant original orientation, at least one of the grooved rollers having crests with sharp edges to form the division between regions A and webs B and to stretch the material to form webs B while stretching the material less or not at all to form regions A. Preferably at least one of the grooved rollers has crests with a waved surface shape.

In the pultrusion of reinforced plastic profiles in strand form, the strands of the reinforcement are brought together in a positioning device and subsequently embedded in the plastic. The pulling of the strands of the reinforcement through the positioning device leads to an unwanted contraction and uncontrolled positioning of the reinforcement in the plastic profile. The invention envisages forming the positioning device by multiple successive positioning means, of which at least some positioning means can be periodically moved forward in the direction of production and also moved back counter to the direction of production. As a result, there is an alternating tensioning and compression of individual regions of the reinforcement. This makes exact positioning of the reinforcement in the plastic profile possible and prevents contraction of the reinforcement.

In the pultrusion of reinforced plastic profiles in strand form, the strands of the reinforcement are brought together in a positioning device and subsequently embedded in the plastic. The pulling of the strands of the reinforcement through the positioning device leads to an unwanted contraction and uncontrolled positioning of the reinforcement in the plastic profile. The invention envisages forming the positioning device by multiple successive positioning means, of which at least some positioning means can be periodically moved forward in the direction of production and also moved back counter to the direction of production. As a result, there is an alternating tensioning and compression of individual regions of the reinforcement. This makes exact positioning of the reinforcement in the plastic profile possible and prevents contraction of the reinforcement.

A method for manufacturing ultrafine fibers having an average diameter of less than 1 urn is implemented by an apparatus including a feeder and a drawing chamber in communication with the feeder via an orifice having a pressure difference. The method includes introducing a multifilament to the drawing chamber under the condition that the ratio of the cross-section of the multifilament to the cross-section of the orifice rectifier is 50% or less, and irradiating the discharged multifilament such that the center of the multifilament melted thereby is located I to 15 mm apart vertically below the orifice outlet to melt the leading portion of the multifilament and cause the multifilament to swing at a maximum angle of 5 to 80 degrees to the central orifice axis within a conical space, such that the melted leading portion of the multifilament is drawn by an air stream generated by the pressure difference.

A method for manufacturing ultrafine fibers having an average diameter of less than 1 urn is implemented by an apparatus including a feeder and a drawing chamber in communication with the feeder via an orifice having a pressure difference. The method includes introducing a multifilament to the drawing chamber under the condition that the ratio of the cross-section of the multifilament to the cross-section of the orifice rectifier is 50% or less, and irradiating the discharged multifilament such that the center of the multifilament melted thereby is located I to 15 mm apart vertically below the orifice outlet to melt the leading portion of the multifilament and cause the multifilament to swing at a maximum angle of 5 to 80 degrees to the central orifice axis within a conical space, such that the melted leading portion of the multifilament is drawn by an air stream generated by the pressure difference.

Disclosed are biaxially stretched polyolefin films containing a) 10 to 45% by weight of a cycloolefin polymer with a glass transition temperature between 120 and 170 C., and b) 90 to 55% by weight of a semi-crystalline alpha-olefin polymer with a crystallite melting temperature between 150 and 170 C., wherein the glass transition temperature of component a) being less than or equal to the crystallite melting temperature of component b), and wherein the polyolefin film has a shrinkage at 130 C. after 5 minutes, as measured according to ISO 11501, of less than or equal to 2%. These polyolefin films are excellent suited as dielectrics for capacitors but also for other applications and are distinguished by a low shrinkage at high temperatures.