Ballistic-resistant molded article

1 . A ballistic-resistant molded article which comprises:

i) a plurality of layers of unidirectionally aligned mechanically fused polyolefin fibers, which layers are substantially absent a bonding matrix or adhesive; and

ii) a plurality of layers of adhesive between adjacent layers of the unidirectionally aligned mechanically fused fibers,

wherein the ballistic-resistant molded article is obtained by a process comprising:

a) providing a plurality of precursor sheets, each of said precursor sheets comprising:

i) at least one layer of unidirectionally aligned mechanically fused polyolefin fibers, wherein the at least one layer is substantially absent of a bonding matrix or adhesive, and

ii) at least one layer of adhesive;

b) stacking the precursor sheets to form a stack, wherein the total amount of the adhesive in the stack is from 5.0 to 12.0 wt. % based on the total weight of the stack;

c) pressing the stack produced in step b) at a temperature of from 1 to 30° C. below the melting point of the polyolefin fibers and at a pressure of at least 8 MPa; and

d) cooling the pressed stack produced in step c) to at least 50° C. below the melting point of the polyolefin fibers while maintaining pressure.

2 . The ballistic-resistant molded article according to claim 1 , wherein the pressure of step c) is at least 10 MPa.

3 . The ballistic-resistant molded article according to claim 1 , wherein the total amount of the adhesive present is from 6.0 to 11.0 wt. % based on the total weight of the stack.

4 . The ballistic-resistant molded article according to claim 1 , wherein step b) comprises orienting each layer of the unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent at an angle of from 45° to 135° with respect to an orientation of the unidirectionally aligned fused polyolefin fibers of an adjacent layer of polyolefin fibers in which a bonding matrix is substantially absent.

5 . The ballistic-resistant molded article according to claim 1 , wherein step b) comprises separating each layer of the unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent from an adjacent layer of the unidirectionally aligned fused polyolefin fibers in which a bonding matrix is absent by a layer of adhesive.

6 . The ballistic-resistant molded article according to claim 1 , wherein the process further comprises, before step a), a step a′) of producing a precursor sheet which comprises:

i) at least one layer of unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent, and

ii) at least one layer of adhesive;

by applying a layer of adhesive to a layer of unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent.

7 . The ballistic-resistant molded article according to claim 6 , wherein step a′) comprises applying from 5.0 to 12.0 wt % adhesive to the layer of the unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent, based on the total weight of the layer and the adhesive.

8 . The ballistic-resistant molded article according to claim 7 , wherein step a′) further comprises consolidating two layers of the unidirectionally aligned fused polyolefin fibers in which a bonding matrix is substantially absent, and a layer of adhesive, wherein the layers of unidirectionally aligned fused polyolefin fibers are separated by the layer of adhesive.

9 . The ballistic-resistant molded article according to claim 8 , wherein step a′) comprises orienting the two layers of the unidirectionally aligned fused polyolefin fiber in which a bonding matrix is substantially at an angle from 45° to 135° relative to each other.

10 . A ballistic-resistant molded article, which comprises:

i) a plurality of layers of unidirectionally aligned mechanically fused polyolefin fibers, which layers are substantially absent a bonding matrix or adhesive; and

ii) a plurality of layers of adhesive, wherein

the total amount of adhesive present is from 5.0 to 12.0 wt. % based on the total weight of the ballistic-resistant molded article.

11 . The ballistic-resistant molded article according to claim 10 , wherein the ballistic resistant article comprises from 6.0 to 11.0 wt. % of adhesive based on the total weight of the ballistic-resistant molded article.

12 . The ballistic-resistant molded article according to claim 11 , which ballistic-resistant molded article has a consolidation parameter (140T16.5-2) of less than 7%; wherein 140T16.5-2 is the reduction in thickness of the plurality of layers of unidirectionally aligned polyolefin fibers which layers are substantially absent a bonding matrix and plurality of layers of adhesive when subjected to a pressure of 16.5 MPa at 140° C. based on the thickness when subjected to a pressure of 2 MPa at 140° C.

13 . The ballistic-resistant molded article according to claim 12 , wherein the ballistic-resistant molded article has an areal density of at most 11 Kgm-2 and meets NIJ level III+ performance against 7.62×39 mm MSC (AK47).

14 . A precursor sheet comprising:

i) at least two layers of unidirectionally aligned mechanically fused polyolefin fibers, wherein the at least two layers are substantially absent of a bonding matrix or adhesive; and

ii) at least two layers of adhesive, wherein

each of the at least two layers of unidirectionally aligned mechanically fused polyolefin fibers which are substantially absent a bonding matrix or adhesive are separated by a respective one of the at least two layers of adhesive which is present in an amount of from 5.0 to 12.0 wt. % based on the total weight of the precursor sheet.