Battery pack and process for the production thereof
A battery pack including a plastic protective layer bonded to the surface of a cell by spreading over the surface of the cell a polyurethane emulsion having a reaction product obtained by emulsifying and dispersing an intermediate product produced from a compound A made of an organic diisocyanate, a compound B1 made of a polyol mixture having not smaller than at least 2.05 average functional groups and a compound B2 having one hydrophilic center and at least two active hydrogen groups in water.
1. A battery pack comprising:
a cell;
a plastic protective layer bonded to the surface of the cell, the plastic protective layer being formed of a solidified polyurethane emulsion; and
a holder assembly fixed to the end of the cell, the holder assembly comprising a first holder and a second holder fitted in the first holder; and
a plurality of output terminals interposed between the first holder and the second holder so as to fix the output terminals in position;
wherein the periphery of the holder is formed so as to follow the periphery of the cell,
the polyurethane emulsion is coated over an outer peripheral surface of the cell and an outer peripheral surface of the holder such that the cell and the holder are connected to each other at their interface by the plastic protective layer coating,
the holder assembly forms an attaching portion and a non-attaching portion, both of which are formed by the periphery of the holder assembly, and the cross-sectional area of the attaching portion is smaller than that of the non-attaching portion, and
the plastic protective layer is coated on the attaching portion and not on the non-attaching portion, and the periphery of the holder assembly is substantially flush with the periphery of the cell.
2. The battery pack as described in claim 1 , wherein the holder assembly is bonded and thus fixed to the cell.
3. The battery pack as described in claim 1 , wherein the holder assembly is fixed to the cell with a rivet.
4. The battery pack as described in claim 1 , wherein a protective element is interposed between the holder assembly and the cell.
5. The battery pack as described in claim 1 , wherein the polyurethane emulsion has a pigment incorporated therein.
6. The battery pack as described in claim 5 , wherein the pigment is a carbon black.
7. The battery pack as described in claim 6 , wherein the polyurethane emulsion having a carbon black incorporated therein is irradiated with a laser beam to display letters, patterns, signs, etc.
8. The battery pack as described in claim 1 , wherein the polyurethane emulsion has a thixotropic material incorporated therein.
9. The battery pack as described in claim 1 , wherein the solidified polyurethane emulsion is formed of a reaction product derived from a first compound made of an organic diisocyanate, a second compound made of a polyol mixture having not smaller than at least 2.05 average functional groups and a third compound having one hydrophilic center and at least two active hydrogen groups in water.
10. The battery pack as described claim 9 , wherein the second compound is a polyol mixture of a bifunctional polyol and a trifunctional or higher polyol.
11. The battery pack as described in claim 10 , wherein the molecular weight of the trifunctional polyol is smaller than the molecular weight of the bifunctional polyol.
12. The battery pack as described claim 9 , wherein the second compound is a polyol mixture of a bifunctional polyol and a trifunctional polyol the average number of functional groups of which is from 2.05 to 2.6.
13. The battery pack as described in claim 12 , wherein the molecular weight of the trifunctional polyol is smaller than the molecular weight of the bifunctional polyol.
14. The battery pack as described in claim 9 , wherein the third compound is either 2,2-dimethylolpropionic acid, and 2,2-dimethylolbutanoic acid.