company union vs trades union

company union and trades union both are nouns.

Word	Noun	Adjective	Verb	Adverb
company union	Yes	No	No	No
trades union	Yes	No	No	No

As nouns, trades union is a hypernym of company union; that is, trades union is a word with a broader meaning than company union:

company union: a union of workers for a single company; a union not affiliated with a larger union
trades union: an organization of employees formed to bargain with the employer

Other hypernyms of company union include brotherhood, labor union, trade union, union.

company union (noun)	trades union (noun)
a union of workers for a single company; a union not affiliated with a larger union	an organization of employees formed to bargain with the employer